Bolbi :
Regarding the second part of your answer, that loophole was closed with Win7. Now it requires the upgraded OS to be activated, which the Vista trial was not.
With Vista, I wanted to upgrade from a 32 bit XP to home premium 64 bit. I bought the upgrade package, and sent in for the 64 bit version. There seemed to be no way to do this, so I called Microsoft support. Since the upgrade package was considered retail, they gave me the following procedure:
You install vista from the cd, but do not initially enter the product code.
Just tell the install which version you bought, and do not activate.
After it installs, you have a fully functional vista for 30 days.
Step 2 is to insert the cd again, while running vista and then do an upgrade.
This time, enter your product code, and activate.
After activation. you may delete the initial version which is named windows.old.
Without a similar such procedure, there will be no way to upgrade a 32 bit license to 64 bit.
There seems to be some confusion on the meaning of "upgrade"
1) The ability to retain your applications and environment. This can be done by loading windows-7 on top of an existing Vista installation. For this type of upgrade, Only vista seems to be supported, and only for 32/32 bit or 64/64 bit conversions, not 32/64.
2) On the other hand "upgrade" can mean that an upgrade package can be used for a clean installed if the user has a valid previous OS. It is the method of validating the posession of a previous OS that I am uncertain about. Submitting the old product key would work, and microsoft could cancel that key to prevent duplicate use. But, if a user needed to reinstall, then it would be a real mess. Submitting an old OS cd would have problems with oem pc's that do not supply one.