i cba to write down a exact guide atm but if u know a bit of comp it shudnt be to hard ... in windows 98 u need to go into ms dos mode (gotta hold sum key down ) dont remem wot exactly tho and then delete stuff off ther .. as i havent used win 98 for a long time now i dno exactly gona try look up a guide for u tho on win xp is rly easy .
1. Go to the bios settings (thts done by pressin delete while comp starts up) and change the first boot device to cdrom
2. insert ur win xp cd to the cdrom and restart ur comp
3. when it says ''press any key to boot from cd-rom'' do it :P
4. follow the instructions given ther.