Sure, it's easy Daisy! Just go to Crucial.com, and use their Crucial System Scanner Tool. No malware, or junk! Doesn't look into your personal stuff! It works! You don't have to buy from them, but if you do, you'll know for sure that it'll work! 100MHz ram is going to be expensive, compared to DDR, or DDR2, (you have Sdram). I feel, but of course I don't know, that your system is maxed out with ram. 512MB's is probably the limit, but Crucial will know. I know money doesn't grow on trees, but how about a motherboard, processor, and ram to match for around $140.00, that has a Intel Pentium D dual core 3.0GHz processor, and 1GB of DDR2,(533MHz), ram? Comes from a very reputable online dealer, Tigerdirect.com.
1.Motherboard/processor combo: http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3311757&CatId=1599 This motherboard can be upgraded in the future to a Core2 Duo processor, it supports them. It has support for up to 4GB's of 533MHz DDR2 ram.
2.DDR2 533MHz ram-1GB: http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1071038&sku=ULT31690 Ultra's good stuff!
You can use the peripherals from your computer now,(harddrive, cd/dvd-rom drive, floppy drive, keyboard, mouse, monitor), and probably your case. The case may be a factor, as I know it's an ATX form factor case, but it might be a mini-tower, so you'll have to do some homework, to see if it'll fit, or email me through Yahoo Answers, by clicking on my icon, and clicking on email. Just food for thought! Yes, you can build it, I assure you! If you want to find out everything inside your computer, hardware wise,(and the OS), such as what motherboard,(maker and model number, plus a lot of other info), processor,(much information), ram, etc., go to CPUID.com, and download the teeny program CPU-Z.