Right after the Bios post, press the F8 key and hold or tap the key every second... the Safe Mode Options list will pop-up, and from that list select the Last Known Good Configuration option.
If that doesn't work, reboot, use F8 and from the options list select Safe Mode... If you're using an account with administrative rights, logon normally and select the System Restore option. If necessary use the Administrator account to logon... when you get to the Logon Screen, press ctrl+alt+delete simultaneously twice to bring up the Administrator account, and if you don't remember the Admin password, leave the space blank and try to logon.. If you can logon, select the System Restore option.