Some computers will refuse to go into safe mode no matter how quickly you press F8.
If you are using Windows XP, here is how to force your computer to boot up with the safe mode prompt:
- Go to START->RUN
- Type 'msconfig' into the box (without the quote marks)
- Click on the BOOT.INI tab
- Check the little box that says /SAFEBOOT
- Click Apply and OK
- Restart your computer.
To get your computer to stop booting up with the options menu, just repeat this process and uncheck the /SAFEBOOT option