For most of us, cost is a major consideration when deciding upon upgrading versus buying a new system. As you look at the cost of the new parts that you want to upgrade in your system, keep a running tab and compare that to the cost of buying a whole new system.

The cost of buying every part in your system and assembling it yourself (upgrading the whole thing) is much higher than the cost of a new system. PC manufacturers buy in bulk and pass their savings along. In addition, a new system will usually come with a complete warranty and software. If you upgrade your parts, the warranty will depend on the warranty for each part.

In general, if the cost of your upgrade starts to approach $1,000, you'll want to look carefully at the option of getting a new PC. There's always a fast new system that can be bought in the $1,000 to $2,000 range. If you decide a new PC is the way to go, be sure to read the later section "What to Look for in a New PC."

If you aren't comfortable opening the case of your PC and adding or replacing things inside it, you won't want to consider upgrades to items such as hard drives, video cards, or RAM on your own. However, for a small service charge, most computer stores will perform these upgrades for you. So, if you choose to upgrade and have the service done for you, factor in that cost of the service to the total of the upgrade.

TIP: Professional service should come with a warranty and a guarantee. If you perform your own video card upgrade and you break it or the motherboard, you'll have to pay for the replacement. Hiring a pro with a guarantee should mean that anything that goes wrong is fixed at their cost.

If you don't want to open the case and you aren't going to pay someone else to upgrade it, there still are a few items you can upgrade or add on to increase the life of your PC and what you can do with it:

If you want to upgrade anything inside your PC, it is highly recommended that you read the book Upgrading PCs Illustrated by Que. This book has many drawings and photographs to show you step-by-step procedures for adding and replacing parts in your PC. Although most of the parts inside a PC are very easy to replace, they can also be very easy to damage if you don't follow the right steps. This book can save you a lot of time and frustration with those processes.

What type of upgrades can you make inside your PC?

Hard drives and CD-ROM drives come in two different varieties. If you want to add a second hard drive, a new CD-ROM drive, or replace a hard drive, you'll need to be sure to get one of the same type that is already in your system.

IDE drives are most common. Unless you specifically asked for SCSI drives when you bought your PC, you probably got it with IDE drives. Most PCs are capable of supporting four IDE drives at one time. So you could have any combination of four IDE hard drives and CD-ROM drives.

There was a time when IDE drives were slower than most SCSI drives. But IDE drives have evolved quickly, and for most uses are now just as fast as SCSI.

NOTE: Some older IDE drives have compatibility issues working with other older IDE drives. If you have an IDE hard drive that is 250M or less and more than two years old, you'll want to consider replacing it with a newer drive rather than adding a second drive. If you do decide to add a second drive, your best bet to avoid incompatibilities is to buy a drive of the same brand as the first.

If your PC does have a SCSI drive connector (either built-in or as an adapter card), be sure to buy SCSI drives. These generally cost more than IDE drives of the same brand and size.

When it's time to upgrade your computer's RAM, there are several memory type issues you need to be aware of. It's important to buy the right type of memory for your PC, or you will have all sorts of odd problems. Or, the PC may just refuse to boot.

A PC motherboard has slots for memory. (These are different than the expansion slots for cards.) The most common of these slots are called SIMM (Single Inline Memory Module) slots. SIMMs come in several different sizes; the most common are 72-pin. These are most common on any PC with a Pentium or faster processors. Some older PCs have 36- or 32-pin SIMMs.

Most PCs have somewhere between four and eight SIMM slots. To decide what memory to buy to upgrade your PC, you should open the case and see how many memory slots are free. If you have no free slots, you will have to replace memory to upgrade. Unfortunately, this situation is common, because many PCs with four slots were sold with all of the slots full.

The most important question in dealing with memory is: "How many megabytes?" Regardless of the number of pins your memory needs to have, the SIMMs can be found in many megabyte sizes. These typically range from 4 to 32M for new RAM. Older RAM that you are replacing may be as low as 1M.

Buying RAM gets tricky at this stage. Even though a SIMM slot may have the right number of pins to accept a PIN, all motherboards have a limit to the number of megabytes that can be on any single SIMM. So, if your motherboard is limited to using 16M SIMMs, don't buy 32M even if they look like they'll fit.

Some motherboards require the SIMMs to be added in pairs called banks. If your motherboard has this limitation (check your computer's specifications or contact the vendor to determine), be sure to buy two matching SIMMs to add the RAM you want. For example, to add 16M, buy two 8M SIMMs.

The next complicating factor in buying RAM is choosing parity or non-parity RAM. Most new machines work with non-parity RAM. Parity RAM is used to check the RAM for internal errors. Again, check your computer specifications to determine which type of RAM your machine requires--then make sure you buy the right type.

Another RAM term you'll encounter is EDO (Extended Data Output). This is a faster type of SIMM that has become very standard in PCs. If your motherboard supports it, buy it. It usually sells for the same price as standard (non-EDO) RAM.

If all of this isn't confusing enough, there are several new RAM types and terms you may encounter. Many new PCs are now shipping with slots for DIMM memory (Dual Inline Memory Module). DIMMs pack more pins (168 instead of 72) and more RAM into just a slightly larger package. If you want to buy DIMMs, be sure to consult an expert first, usually a qualified technician where you bought your PC. DIMMs have a dizzying array of voltages and other specifications in addition to memory amounts, and buying the wrong type will cause problems.

CAUTION: Don't purchase "cheaper" slower additional RAM. Additional RAM must be at least the same speed or faster than the machine's original RAM. Mismatched speeds can cause system problems.

Another new type of RAM is called SDRAM. Like EDO, this is a faster kind of RAM. Unlike EDO, SDRAM is currently much more expensive than standard RAM; unless you are a hard-core computer speed addict, it isn't worth the extra money.

If you are going to install a new card into your PC, you need to know what kind of slot it will go in.

There are two slots that you will find in most current PCs. The first is an ISA slot. This is an older standard and is slower than the other type. But, for many uses, it is still more than fast enough. Cards that you'll probably want to buy ISA versions of include:

NOTE: If you have an older PC, you may find that you have two different types of ISA slots. One is a short 16-bit slot and the other is a longer 16-bit slot. If you have a system that has 8-bit slots, you can only use 8-bit cards in these. Eight-bit cards will work in either 8- or 16-bit slots, but you'll want to save your 16-bit slots for 16-bit cards.

The other kind of slot is a PCI slot. Most PCs now have three of these. These slots are much faster at transferring information from the card to the processor than ISA. They also have the advantage of working better with Plug and Play. Cards that can take advantage of PCI slots include:

Before buying any card, be sure to check the PC to see that there is a free slot of the right type. If the card is a replacement, remember that you will be able to use the slot currently filled by the old card.

NOTE: Before there was PCI, there were two other types of fast slots. One was MCA and the other was Vesa Local Bus (VLB). You won't find these on any new PCs, and if you need to upgrade a card in one of these, you may have trouble finding them. If you are considering upgrading a machine with either of these, replacement is probably a better option.

Adding and replacing expansion cards and peripherals in your PC is not easy. Most cards have small connectors called jumpers that determine what system resources the card will use to communicate with the PC. But no card can use all system resources. These resources are limited, and configuring more than two cards to work together can drive even experienced PC upgraders crazy.

So, Microsoft and several hardware vendors established a new system called Plug and Play (available with the release of Windows 95). The theory is that you plug the new card into a slot or plug in the new peripheral, and when you restart the computer, Windows and the motherboard BIOS find the new card and configures it for you.

In order for this to work, your PC has to support Plug and Play and you have to buy hardware add-ons that are labeled as Plug and Play (PnP) compatible. The bad news is that if your system is more than a couple of years old, it definitely won't support this. And while there are a lot of PnP devices available, there are also a lot of devices that aren't PnP. If you have several older non-PnP cards in your PC, these may cause Windows trouble when trying to configure PnP devices.

If you are shopping for new cards, there are a couple of things you'll want to be sure to look for PnP varieties of. First is sound cards. Sound cards can be the most difficult addition to a PC, and Plug and Play can be a huge help with them.

You should also look for PnP varieties of internal modems. If your PC has built-in serial ports and supports PnP, a PnP modem is much easier to install. There are also so many modem varieties that it can be hard to find the exact correct model in the Windows modem setup if you don't have a PnP modem that Windows can identify for you.

Some devices such as hard drives, keyboards, and mice don't need to be PnP. Printers, monitors, video cards, hard drive interface cards, CD-ROM drives, network cards, and scanners all come in PnP varieties.

Unless you enjoy the work of upgrading your PC and adding on to it, be sure you get everything that you want in your new PC when you buy it. Here are some guidelines for what to look for.

All of the items in this first list are essential must-have items for your new PC:

In addition, here's what to look for in other optional equipment:

There are two main options to look at when buying PCs or parts. You can buy them from any local store that sells them, or you can buy them from a mail-order (direct) outlet.

The advantages of buying from a local store usually involve convenience. If you want the security of seeing the PC or part before you buy it, or knowing that you can return it or have it serviced by simply driving to the local store at the mall, buying locally is for you.

TIP: When shopping for a new monitor, I almost always recommend buying it locally rather than mail-order. You'll want to see what the picture looks like on-screen as monitors with all of the same technical specifications can have dramatically different picture quality. You can't see that in a magazine ad or over the phone.

Buying locally usually gives you a chance to test-drive the system in the store and ask a helpful sales representative questions about the hardware. A little common sense goes a long way here. A lot of stores sell PCs now. Chances are the salesperson at the local PC store will be able to answer more of your PC questions than the salesperson at an electronics store who also sells refrigerators and TVs, or the salesperson at a department store selling everything from underwear to computers. The bottom line is, shop where you feel most comfortable.

The big advantage of buying from a mail-order or direct outlet is usually price. You will be hard pressed to find a local retail store that can sell you a new system with all of the same features as a mail-order outlet for the same price.

Buying direct also has the advantage of having a much larger selection. If you like to have a lot of choices, call several mail-order outlets and compare their offerings. You'll always find a better selection than at the local stores.

A final advantage that most major mail-order retailers have is a better trained sales staff. For example, when you call Gateway or Dell's order lines, the person that answers the phone does nothing but sell computers. Before they ask you technical questions about what type of processor you need or how much RAM you want, they do a good job of finding out how you plan to use the system so that they understand your needs. Gateway and Dell aren't the only ones; any of the major PC vendors who sell direct can help you a lot when buying a new system.

When buying parts through a direct channel, I recommend picking up a copy of Computer Shopper magazine before buying. Any computer store carries this massive magazine, and you can find dozens of reputable dealers listed there. For about $5, this is a great investment in the most up-to-date information about who's selling what for how much.

There are several things about buying a new notebook that are different than buying a PC. Here's a quick list of additional or different features you'll want to look at in a notebook.