|"how do i disable graphics on intels core i processors"|
The processor has nothing to do with enabling or disabling the graphics. Usually integrated video is disabled in the motherboard BIOS menu but there may be several settings that need to be changed - enable/disable, shared memory, intial display. Some boards auto-disable the integrated video when a card is detected. Every board is different. Your manual should explain how it's done.
"what core i processors are compatible with XP"
I believe all of them are.