OH DEAR --PLEASE GET YOUR FACTS RIGHT.
THERE IS A 32 BIT VERSION OF VISTA ULTIMATE - in fact the retail edition came with BOTH versions on the DVD (even the Upgrade version).
For VISTA HOME PREMIUM you could always get a 64 Bit edition - you just had to send off (Via the Internet) for the DVD -- the Key was the same as your 32 bit edition. You just had to pay around 3 - 5 EUR for the media.
(This applied to Retail versions -- not Pre-installed OEM versions).
In the present climate BTW when buying a Computer with a pre-installed version of Vista always ask the store manager to throw in a retail copy of Home Premium. They will often oblge to make a Sale.
Here's a screenshot from a Laptop where I'm running Vista Ultimate X-32.
Cheers
jimbo
You are right on the money here regarding the fact that Vista Ultimate (upgrade or full retail) came with both versions...

And yes, you could obtain a copy of the 64 bit version simply by ordering one online from the site MS gives you on a little card in the packaging of all Vista's below Ultimate.. And your right the key for the 32 bit version worked for the 64 bit media as well...
On a side note though, it's incorrect to label a 32 bit edition of something as X-32...

It's x86 and x64.. I'm not trying to be a d!ck.. I just wanted to point that out as you asked the op to make sure he had his facts right...

I apologize if this offends you in any way, that is not my intention....