Although I did try and have a look see at your problem microsoft doesn't seem to have a lot of info available in their "knowledge base" or as far as I could tell.
Here is the link from where I did a bit of searching. It might be wiser to try to use a more robust and supported application such as VMWare . There are tutorials here on how to use vmware and backtrack. These might be a better solution for you.
Also the usual things like checking the md5sum of the download might be useful.



