This is from the Owner's Manual of Dell Dimension 3100:
Using Dell™ PC Restore by Symantec
Use Dell PC Restore by Symantec only as the last method to restore your operating system. PC Restore restores your hard drive to the operating state it was in when you purchased the computer.
Any programs or files added since you received your computer—including data files—are permanently deleted from the hard drive. Data files include documents, spreadsheets, e-mail messages, digital photos, music files, and so on. If possible, back up all data before using PC
Restore.
NOTICE: Using PC Restore permanently deletes all data on
the hard drive and removes any applications
or drivers installed after you received your computer.
If possible, back up the data before using PC Restore.
To use PC Restore:
1 Turn on the computer and watch the keyboard status lights.
2 Immediately upon seeing the lights flash, press <Ctrl><F11>.
If you do not press <Ctrl><F11> in time, let the computer finish restarting, and then
restart the computer again.
NOTICE: If you do not want to proceed with PC Restore, click Reboot in the following step.
3 On the next screen that appears, click Restore.
4 On the next screen, click Confirm.
The restore process takes approximately 6–10 minutes to complete.