Software

Boot with a win98 floppy boot disk with cd-rom support and re-install Win98 on top of your current installation. It will replace any missing Windows files and your should should boot normally thereafter.

Open the case and see if the graphics card is set correctly and check the memory modules to make sure they are seated,sounds like it could be a graphics card problem to so check it and reinstall the updated drivers

If it happened suddenly then it is either a hardware problem or it sounds to me like a virus.

Use a PC with virus protection to create a virus scan boot disk and scan the PC for a virus.

This question was auto closed due to inactivity