If you REALLY have no further use for the old computer, you can just
harvest it's hard drive, and either (a) use it as a secondary drive
inside your new computer, or (b) put it in an external hard drive
cage.
Then you can sell the old carcass on ebay, or donate it to charity.
Or just throw it away. A 98-vintage computer, with no hard drive, is worth
next to nothing.
I'd keep the keyboard, mouse, and monitor as emergency spares.
But I think your suggestion is a good one. Just using the drive makes much
more sense than networking the entire old computer. It saves space and
electricity, won't require parts to be fixed or relaced as they wear out,
etc. It's also much easier.
The only thing that Flo should be aware of, though, is that if the drive is
really small (and it may be if it's from the Windows 98 drives) it probably
doesn't pay to invest any money for a hard-drive enclosure for it.. If it's
not 10-20GB at a minimum, it may not even be worth keeping.
I've got a couple of old small drives like that sitting around that I
haven't used for anything. I'm theoretically saving them so I can give them
away to someone who wants them, but it will probably never happen and I'll
end up throwing them away.