You used to be able to do that with Win 98, but they killed that loophole in Win Me.  I am fairly certain that with Win XP you can only do an upgrade with the upgrade version.  Probably in response to how angry the people were who paid $109 for a full version of Win 98, only to find out that you could do a full clean install from the upgrade CD for only $90.

>It has been advised, for best results, particularly with WinXP, format,
>and do clean install of new OS, rather than install upgrade over the top.
>What if have upgrade version, to save money; format, and do clean
>install?
>
>
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