I don't think it would. If he's just reinstalling XP, it should put it back on, shoudln't it? And if he's just taking it off so he can boot Ubuntu on the drive, he'd just have to take the XP option out of GRUB.
When at the disk selection screen for Widows just delete all the partitions and then it will be a Raw disk. From there create just a single partition to a sized partition that you want for XP and format it and install.