VirtualBox can be configured to present an custom ACPI table to the guest. Use the following command to configure this:
VBoxManage setextradata "VM name"
"VBoxInternal/Devices/acpi/0/Config/CustomTable" "/path/to/table.bin"
Configuring a custom ACPI table can prevent Windows
Vista and Windows 7 from asking for a new product key. On Linux hosts,
one of the host tables can be read from
/sys/firmware/acpi/tables/.