If it is from some vendor, Dell, HP, etc, use this:
http://forum.notebookreview.com/showthread.php?t=144783
The key provided on the computer is "fake" in that it has never been used.
Instead, vendors use two special files to license and activate your copy of
Vista. This procedure will simply move those two files to your re-install of
a different bitness. It still has the be the same machine since those files
are tied to that machine.
"Talek" <Talek@xxxxxx> wrote in message
news:B0763D91-DEF1-4529-BA3E-B106F000218E@xxxxxx
Quote:
> Hi, I purchased two copies of vista, one 64 and one 32. The 32 bit was
> installed on a different machine and the 64 bit on my own. Since then I
> have
> found 64 bit to be rather incompatible with my needs.
>
> I am wondering if I can reformat my computer with 64 bit on it, then
> install
> the 32 bit software on it using the 64 bit product key so I don't use the
> same key twice.
>
> Since I only have OEM, I am wondering if my 64 bit key would be compatible
> with a 32 bit copy of Vista. Anyone know? Thanks