rmrf -- can you explain how this is piracy?
I'd just like to know because on the surface it sounds ok to me. He says he has a [ presumably legally licensed ] copy of Win98 and is asking if he can use that to upgrade to a [ legally purchased ] copy of winxp pro. According to the link you provided, yes he can use the win98 disk to upgrade to win xp pro.
[edit] perhaps the original question is more specifically stated as "when I activate my win xp pro upgrade, will it matter to MS that I used the same win98 disk as when I activated my win xp home upgrade?" -- don't know that answer, but I don't think MS would care. I think the upgrade simply says you must have a legal copy of a previous OS, not that you have to have a unique copy of a previous OS.