I've already mentioned before that I feel that Windows 7's Boot From VHD feature is the best new feature in Windows. But what I also really wanted to do was to be able to take the VHD, put it on a USB storage device and boot from there.

And after trying and failing for a few times.. finally I've done it! The summarized process is.

1. Install Windows 7 Ultimate on a VHD. (search the net, plenty of ways to do this)
2. Read through this document to prepare Windows 7 and the USB drive for booting.

It's actually quite simple, a bit complicated though. I'll prepare a more detailed report once I finish some more testing.