XP upgrade?

You know the 'upgrade' version of XP?

Well, say you had bought 2 of them... but you used the same 98CD on both to prove that you had 98. Would activation catch this?

When you install it it asks for a 98 CD (to prove that you have 98). But the disc is in-fact a full XP Home install.

Don't want to buy it otherwise, and I'm not going to use a pirated corp ver.