oh, and i really hope you don't have a problem with the key.
that can be a pain in the ass.

make sure you have the right copy of your OS.
Vista doesn't matter, everything is on one cd.
XP is different.
If you have home, you must use a copy of home.
If you have pro, a home cd and pro key will not work, and vice versa.
If you happen to stumble upon a Volume license cd, that will not work.
if you happen upon an OEM cd, that will not work.
and the best news of all, there is no way to tell what kind of XP install CD you have besides installing it.
If there is, someone please tell me.