My set up is; 120gig HD on IDE-0, CD Rom(Master) CDRW(Slave) on IDE-1.
You are right in seperating your HD & CD's onto differnet IDE's as they will only work at the slowest part.
I tried XP on an AMD800 and didn't like it as it was too slow, so your CPU may not be powerful enough for XP. That was with 512RAM.
You also say you have two HD's on IDE-0 is one of them an old slow HD, if so you will find they both run at the speed of the slowest HD.
Try running msconfig and de-selecting anything that runs up on start-up but you only use occassionally. MS Office and OCR software is one which I would de-select. They will load anyway if you need them.