Windows XP Home Discs knackered!?

I use Windows xp Home and bought the pc it is connected to 2nd hand. The problem is my second disc is unreadable now for some reason which means that I have had to find the drivers i needed and added them myself (i still dont know if i have the right ones) I dont know what else that I need to do. My question is can i replace the 2nd disc somehow (somewhere) OR would it be easier (cheaper) for me to but a cheap 2nd hand pc and use the registered disks from that. I know I can download from a peer/seed but I'd rather keep 'legal' if not too expensive. (its gonna be 80 quid or so I think for a new xp!)