i would also reccomend reformating to clean the drive up if not for anything else.
but you dont need the full xp disk if you have the me disk just buy the upgrade.
some people ive met seem to be undeer the impression that it actually takes files from the me disk and installs them into the OS. This is not the case, the me disk is must be inserted simply to verify that youown the disk, while all the data ome from the xp upgrade disk