User:Mach4cs

If Vista or XP won't start

Reboot the computer whilst holding down the F9 key.

This allows booting into 'safe mode' by pressing the F8 key.

Be patient, it will slow down the computer.

When the system has started in safe mode:

Start - programs - Accessories - System Tools - System Restore

Choose the option offered of the most recent restore point.

Be patient! The system will reboot to the previous configuration.