Hands-up, this is a depth of working on Win7 and 2008 R2 which I do not expect to explore. However, I can appreciate how useful this post from James O’Neill is, so I thought it worth linking here.
Booting from VHD (and some gotcha’s) will be a useful feature for all sorts of reasons. If you read that post and think “Oooh, that sound like a bit of a wheeze, I could try that” then YOYO and perhaps you should probably wait for his explanatory video?