If you are using any form of original Mac system less than 9.2.2, you should cut your wrists right now.
Filesharing, and cross-platform networking works a treat in 10.2 (Jaguar) but even better in 10.3 (Panther) and 10.4 (Tiger)
We have 8 Win PCs and 2 Macs hooked to a Linux server - it's no perfect, but it's not bad either...
NOBODY uses System 8.00, it's deader than Breakdancing...
If you have Win XP, you should be able to set up one comp as a server and create shared folders, plus the same on the Mac, IF you have 10.2 or better. Remember to set Domain, Workgroup, Password etc and you should be able to get it running.
OSX supports everything you need, I say again: Upgrade! because your head will hurt if you don't...