sarce03

Good day! This is my first posting ever, although I've always been able to work out many problems, this one is not as easy. And an important note: I am a single dad (2 sons), which means funds are prioritized and tech advances are past what I use, but I have to make due. If this means limited help-sorry and I understand.
Now-
Last year, my PC went down-I had to utilize my old PEN II with purchased W98 on HD which I was saving for my son (9yrs. old) and what I figured out on my own, was the steps to get my HD with Win XP pro installed to this PC which having read up on this I now realize is tricky. Score 1 for the poor man. Again PII had Win 98-purchased on HD which is saved/stored. The HD in PC that died had Win XP Pro upgrade with all my stuff which I transfered. I'm not an expert user, just better than a novice really and there's much I've learned but not a lot.
The ex-wife gave me another PC, Powerspec 7530, Supermicro 370SSM PEN III, Intel 815 Solamo chip set (82815 GMCH/828801 AA ICH) with a Western Digital WD400 (40 gig h/drive) 512/133mhz ram and no computer disks, not available. Tried putting XP pro upgrade but it didn't work. And the steps I originally did was from 98 to XP pro upgrade. Read your past answers and got some startup boot disks (freeware)Win XP-98-95 downloaded all just to have them, and used one, got it to boot; it said "starting WIN 98" at one point established the ability to reload XP got the F: or whatever ltr prompt, everything seemed to be possible, then when I tried, it said it couldn't access or something like that, I imagine the lack of drive info on HD was the cause. I tried scandisk to view it, and it said it couldn't access the HD, although it shows in the bios as a valid drive C:. At this point I searched out, went to the MB site and downloaded some files for configuring the drives for the MB that are recommended upgrades because that's all I could do.
I'm thinking without the drive info already placed onto a partitioned drive space on the 40 gig HD thru formatting, I'm getting nowhere but how to do it without the disks;

can I put it as a 2nd drive on my PII and download the drivers needed and then replace it back in the PIII and start over? Me thinks no.
Or is it possible I can put my HD in the PIII that won't endanger my programs and personal work on it as this is crucial to protect (musician/recordings), for this reason I did not do this first. I figured too risky.

So, I want to get my current stuff on that PIII w 40 G HD. And my 98 disk is lost now having loaned it out, was never given back. I want my son to have his PC for educational purposes too. Is this clear? I've tried to cover everything as best I can. Am I out of luck and wasting your valuable time? If so, apologies, I'll see what else is possible, but if you can help-please do-this PII sucks so bad, I'm in slow mode torture here.....thank you kindly for reading, I hope there's no trouble.
Steve