32bit Vista ---> 64bit Vista

I've read some threads here along with some faqs and reviews on Vista, but there is something I can't figure out. If I wanted to go from Vista 32bit (OEM install) to a Vista 64bit, would I have to buy a full version of Vista, wipe the 32bit and then install a clean version of the 64bit? The discs for both bits come with the full versions, correct?

I've searched on Newegg, but there are so many versions that they are selling I have no idea what I'd need.

Such as:
- Microsoft Windows Vista Home Premium Upgrade - Retail
- Microsoft Windows Vista 64-Bit Home Premium for System Builders Single Pack DVD - OEM
-Microsoft Windows Vista Ultimate Upgrade Signature - Retail
- Microsoft Windows Vista 64-Bit Ultimate for System Builders 3 Pack DVD - OEM
- Microsoft Windows Vista Ultimate Upgrade Tech SKU - Retail

A few of the descriptions also say that the 32bit is included but that there are instructions on how to obtain a 64bit version for some extra fees. No clue what that means exactly. Shipping may be a bit of a problem for me (APO address), and I don't want to wait around for the mail to run its course.

The bolded sections are what confuse me. I appreciate any input.

 

retail = 32 & 64 bit OS's, but usually just comes w/32 bit and you haveta get MS to ship u a 64 bit cd u pay shipping ><

OEM = can't change the OS from computer to computer, but ALOT cheaper, also it's 32 bit OR 64 bit OS

The Upgrades are usually cheaper and require you to have a previous version of windows, I believe System Builder's Pack = for people making their own desktop/notebook systems it has the full OS just OEM.

 

You'll have to pay for a full version of 32bit, then order the 64bit media from Microsoft. From a compatibility point of view, it is still better to stick with 32bit.