That's because XP RTM doesn't know if it's genuine. XP SP2 does. Vista
must install on a "genuine" install of XP.
"Dweebs" <dweebken@yahoo.com> wrote in message
news:8B7AC769-6F53-45F5-AF6E-F3BE5DF0F55F@microsoft.com...
>I tried installing Vista over Win XP RTM (no SP1 or SP2). Vista told me to
>get lost, as it needed XP with SP2, so I had to download and install SP2
>just to load Vista on a clean install. There's nothing on the ungrade box
>that says it neexs SP2 - the upgrade box just says XP, so as far as I'm
>concerned this Vista upgrade information on the box was false and
>misleading for me.
>
> Regards,
> Dweebs
> "MICHAEL" <u158627_emr@dslr.net> wrote in message
> news:%23hJcv4bYHHA.4520@TK2MSFTNGP06.phx.gbl...
>> http://windowssecrets.com/comp/070308/#reade1
>> Most of my readers thought it was highly interesting that Vista doesn't
>> perform even the simplest test for a qualifying operating system before
>> the upgrade version will install. Any running Windows OS, from NT 4.0 to
>> Vista itself, will do. Vista's complete lack of any version-testing code
>> makes it possible to clean-install the upgrade version of the new OS to a
>> blank hard drive - a capability that Microsoft claimed it had
>> deliberately eliminated from the product.
>