That is a very standard IDE drive that you can replace with just about any IDE drive you can find, at least to get things up and running. The controller won't support the faster transfer speeds of later drives, and may not support the full capacity of the larger drives, but the newer drives should be backward compatible. Something in the 500MB range would probably be a good choice. Also, looking at the information I have on the motherboard the drive controller can't be disabled. You may be able to add a secondary drive controller, but booting from the hard disk on that controller _may_ not be possible.
On the old 386 era PCs you have to specify cyl/head/sector/lz type stuff in the BIOS usually? It's possible to sub in a CF card on the IDE bus with a cheap adapter, but I'm not sure how the cyl/head/sector stuff plays out. Maybe go with something fairly small like 32MB and a CF to IDE adapter (it's just wires, CF cards are similar to early PCMCIA which is ATA which I think is just buffered ISA but I could have it wrong?)
I did this recently on a 486 but it had an auto-detect feature for the hard drive parameters. Maybe they don't really matter when using a CF Card -- does anyone know?
Another option is the ISA CF/IDE card from GlitchWorks. It has it's own BIOS AFAIK and you don't need to worry about specifying the drive info in the bios. I have 3 or 4 but haven't tried them yet.
On PCI systems Promise FastTrak IDE cards take care of the BIOS drive specification annoyances -- I use a PATA IDE to SD card widget on a FastTrak 100 on my Pentium luggable -- works well.
-- : Ethan O'Toole
