Win 98.....LOL......that is really stone age thinking......if you want to be a masochist, then trying to work with something that harks back to the "good old days" will only give you headaches galore......time to revamp the whole system and bring it up to date with modern peripherals......the basic hardware is probably good to go, if it's not already worn out hence the auction scenario, but the electronics are another matter......my opinion only.
I'm not sure if you can do this, (not all that computer literate at all) but you "could" pull the hard drive out of the '98 computer and install it as a slave drive in a Win XP computer....or whatever you have.... and then access the files on it........but using the new host computer to do the boot up......BTDT......you can then load Mach 3 to the new host computer hard drive.
Ian.