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.

people buying windows, in my /comp/ ?
as for 62nds.com, i keep hearing well from it, but i dont really trust it, not until the day i get to use it and reverse engineer it myself, the main reason i dont trust it is because of the weird type of extensions it wants to install to be used.