I'm assuming you have a fairly recent version of Windows.
Hold the "F8" key down as the PC boots up. If your windows installation isn't completely screwed you should get to the safe mode prompt.
You can then access Windows using safe mode and fix your problems.
If that doesn't work you could try a repair using the windows installation CD that came with your PC (if it came with one).
Boot the PC with the CD in the drive and follow the prompts. If your PC won't boot from the CD you might need to go into the BIOS and allow boot from CD. You can access the BIOS by pressing del (usually) as the machine boots.
If the above doesn't work you could reinstall windows (if you have the cd) and providing you have no hardware issues. Use the same process as above but reinstall instead of repair.
Jeff Hooper, January 2011
