I want to upgrade my hard disk. I run windows xp but the store had drives as large (or larger) than 1Tb. Can windows xp support drives that large or should I get a smaller one, say 500Gb?
You should be looking at around 144 petabytes as a limit. Highly doubt you need that much space, or even have the money for that much space. Get what ever size you want. As long as your BIOS is compatible with 48bit LBA.