You never want to install an OS on a USB hard drive. They are very slow compared to an internal hard drive.
Using a USB drive won’t get you past the drive problems. You will still need drivers for that OS.
Installing an OS replaces the GUI from the previous OS.
What is the end result that you are trying to get to?
What’s the answer to the question posed in your <a href=”http://itknowledgeexchange.techtarget.com/itanswers/vmware-for-windows-vista-virtual-tool/”>other thread</a>?