Changing the appearance of cleared activities
You can set a personal preference for changing the appearance of cleared activities. This setting makes cleared activities easier to notice in a list of activities.
To change the appearance of cleared activities
From the Tools menu, click Preferences.
Click the Calendar & Scheduling tab, and then click the Scheduling Preferences button.
In the lower portion of the Scheduling Preferences dialog box, in the When clearing activities box, select Strikeout to have a line drawn through the text of the cleared activity.
or
Select Gray to have the text appear gray for the cleared activity.
Click OK.