Posted 09 June 2010 - 06:43 AM
You say you've changed the monitor and thats made no difference it sounds like the graphics card is giving up the ghost. I don't think you will find many new graphics cards suitable for Win98 but you may find some on eBay.
You could try starting up in Safe Mode that only uses basic settings and drivers to get Windows to run. Keep the Ctrl pressed until you see the boot menu then select Safe Mode and see how it shows once Windows has started and gone to the desktop. You could try downloading new graphics drivers just in case your have been corrupted.
Windows ME (spare computer)
Windows XP 2002 Professional SP3 (desktop computer)
Windows 7 Professional SP1 32bit (laptop computer)
Windows 8 64bit spare drive for laptop computer