Well, check the HP support website and find your model# PC and note down all the specs. You're windows is XP for now and ever as that's as far as it will go. Add all the ram it can handle and probably increase HD size maybe to 80gb or better, if you like. Sorry, when it comes to OS installs you need to provide the drivers and HP support should have what came with the system. Otherwise, know what is present and find the proper drivers for that product, XP drivers. Its not that hard overall, but you do have to assure you're getting the right ones. If you're willing to spend $, then consider that this will be better spend on a true P4(2.4ghz or better) or even dual core if you find one.
If you like check out the use of Linux OS, such a Ubuntu. Use the live version that runs off the CD in order to get a feel for it.
IMHO, you may have picked a too old of PC other for playing and getting to know more, education in the making. I just think you're not going to get a hot PC out of this other than for learning. Check your local Craigslist or eBay for other offering. Craigslist, you can put search or request if possible. Also FreeCycle maybe active in your area, post there too.
I recently purchased a computer at a yard sale, (working but hard drive swiped clean) . . . an HP Pavilion 6830.
Hardware includes: Intel Celeron 700 MHz processor, 20 GB hard drive, integrated graphics (Intel 810L), 2 usb ports, and the max. of 512 MB ram.
It's designed for Windows ME which is no longer supported and I was wondering what would be the best os for such a beast. I also added an ethernet card but I still don't know hardware and driver specs of it. I have two Windows Xp disk but would prefer something that automatically detects drivers during install. Please help.