Does that mean that I need to clarify?
<b>Procedurally</b>, I would never, ever upgrade one kind of Windows to another. I have yet to see a Windows upgrade program that doesn't cause problems in the resultant system. You're going to find yourself spending time tracking down funny stuff if you install XP over an existing 98 system, so why not spend that time doing it right in the first place?
<b>Media</b> is a different matter. If you own a full (not an upgrade disc) copy of Windows 98, you can save some money by purchasing the retail upgrade version of XP. If the upgrade allows you to start with a blank disk (I haven't tried), then you get the benefit of the optimal install <i>and</i> save money. I've been spoiled by having the full MSDN versions available to me, but if I was trying to save money, I suppose that I'd get the upgrade version. MS has enough of my money for now.
You are false data.