Were there any beeps on bootup, Russ100? Can you hear any sounds from the tower when you switch on, any sound from the fans or from the hard drive spinning up?. It does sound like a hardware failure, either the PSU, memory, graphics card or hard drive.
Getting into the BIOS on Win98 is usually achieved by holding down the Delete key at bootup, Russ100. From what you've said so far, it's looking like a hard drive problem, You will probably need to open the case and check all the cables, make sure they're seated correctly on the motherboard and connected firmly to the hard drive. When you're in there see if you can hear anything from the hard drive when the PC is switched on. Also take a look to see that the CPU fan is working. Also try the hard drive in another computer as a slave to see if it can be accessed?