Am I being conned?

I'm replacing everything except for my HD, according to a *i know everything about everything* friend, I don't need to buy another copy of XP, but according to the Sales guy, I do.

Who is telling the truth? Seems pretty silly to me to have all the OS files on my HD and not being able to use them.

It is highly likely that when you transfer your hd over and then boot XP from that disk, you will need to reactivate your copy of xp. You probably don't need to get another copy of xp