Hmm workable... it depends if what you have now is what you'd call 'Workable'...
What processor, RAM do you have?
First try running Disk Cleanup from Programs, Accessories, System Tools, and let it remove what it finds (none of this is important, though if it finds any 'Old Compressed Files', or 'Compressed Files', take the tick off them) and this will clean up your system no end (if you've never used this, it might take a while)
Next you need to run 'Scan Disk'. In Windows 98, this should again be in System Tools, though after it crashes, this would probably run anyway.
Then run Disk Defrag which is a good thing to run and might just give it the kick it needs as it defrags the whole drive and stores everything where it needs to be to make it easier to access data.
Find this in Programs, Accessories, System Tools too
Note that it might take a while... especially if you've never used it before (approx, a few hours, or more since it seems like a slow PC
So leave over night).
It might also work best if you put it in Safe Mode (f8 at bootup, and select Safe Mode from the list), and then run Defrag as it has more access to resources to do its job.
Hopefully these will speed the computer up for a little while, though nothing would speed it up more than a full format and re-install of windows, since your computer seems to have took a good old beating
If you were to want to format then re-install, you'd of course have to back up first, and you could do this by use of external drives (Like music players), or well...I guess you won't have a CD recorder, though if you do, this would also be a good option.
I hope this helps