Vista Home Premium 64 to Ultimate 64

The upgrade is fine to use to go from Home Premium to Ultimate.
To go to Windows 7 though, its recommended to do a clean install (this goes w/ every major OS upgrade) if you just upgrade, you'll wind up with lots of legacy files and systems still on your computer.
Why do you need Ultimate anyway?
its real advantages are BitLocker Drive Encryption, and Ultimate Extras. Both you can find online through either hacks (aka hacking to get Dreamscenes, very easy to do) or 3rd party applications that are free or cost less

Just guessing, but Vista Ultimate will support VM. Home premium does not. I'm helping someone with their build with the same situation.

I need to be able to install XP Professional in a Virtual Machine since my companies VPN and other applications don't work with 64-bit applications. I've read mixed things about being able to install Virtual PC 2007 on Home Premium. I know you can bypass the install error messages but I've seen differing posts on the success of it running well.

Use the MS anytime upgrade... that would be the simplest way I believe. Other than that, buying a retail upgrade package is the next best thing. It all depends on which is cheaper...

On an Vista Home Premium 64-bit system, you can go through the process of looking at the Anytime upgrade but then you get to a point where it says, 64-bit DVD is not included in the anytime upgrade. Supposedly, you have to receive the 32-bit DVD and then fill out the included form for a 64-bit DVD. Both of which you have to pay shipping for. Shouldn't the Upgrade Advisor know it's a 64-bit OS? But even more importantly, why is Microsoft not offering to ship the 64-bit DVD to a 64-bit OS owner?

VMware works fine on Vista home 64. That would be my choice using the free player.