If it's a fried Motherboard then you're OK. Buy a new MOBO & HDD and Slave in old HDD and copy data. You can then use old HDD as additional storage. (You'll probably need to get a new HDD in order to install a new copy of OS as old version will use older/incompat versions of North-Bridge Chipset Drivers, despite using same OS to re-install - installed during the Blue pages of a Win XP install)
If it doesn't have a Firewire, then get a PCI card (I have an old 2+1 card after I upgraded it to a 4+1 USB2/2+1 Firewire card combo to save on slot usage - +1's are internal)
If it's a HDD problem, then just get a new HDD
Yes, It is a nause to re-install all OS, software & personal data (if backed-up) on first failure, but you won't allow it to happen again!
Try
Spinrite to retrieve data from old drive (installed as a slave)
Get a second HDD and make regular backups of personal data! (or set up a raid array - something which I've never understood how to set-up!)
If it's memory, then
MemTest is your tool. Buy new memory! Your profile doesn't portray your location, but try to keep it cool.