You may run into issues with Microsoft who have built heavy copy protection into
Vista. It is likely to detect that it is not running on the original machine and
spoil your plans. While technically you are running it on the same machine, MS
does not see it this way. You are making a copy of their OS and this is not
allowed. They may have a license that allows virtualization, but if it exists it
is likely to be pricey. There are several ways to get skirt copy protection on
Vista and they can be googled on the net.

There are ghost tools available for Linux such as G4L or SMART. I am sure that
it can be done, but you may need to bone up on your skills to do it. I know that
forensics experts do this to recover information from computers that are
destroyed or wiped clean to recover information or evidence.

If your plan does not work out and you elect to go for dual boot, keep in mind
that it is harder to set up dual boot with Vista in the first place. If you need
to recover your Vista drive as some OEMs have their computers set to do from a
recovery partition then they have the habit of wiping out other partitions to
restore the original set-up. Finally Vista SP1 is said to destroy Linux
partitions. I do not use Vista, this is only what I have read on the net.
Perhaps someone with first hand experience can share their knowledge.