Sounds like someone tapered with your computer while you weren't looking lol

You may need to perform a system restore to get control back.

You can restore the system by placing your windows CD in the CDROM drive normaly drive D:

Restart the computer

Go to your BIOS

Make sure the boot sequence is set to

1st Boot Device - CDROM D:
2nd Boot Device - Primary HardDrive C:
3ed Boot Device - Floppy A:

Or CDROM,C,A

then save and exit

restart the computer

you should see ( Windows is now starting your computer )

and the install process will begin.

once windows is installed and you've put your key in

you should go to the windows update site to download ALL critical updates and service packs

Then you'll want to load driver software for your computer,

Az