Some others have seen this problem before as well... You probably have an existing SQL Express installation on your machine correct?
If you have the security policies set on that SQL Express instance to require a strong password that is X characters long then the password used by the VS install doesn't match that criteria the install fails.
Easiest thing to do is disable the your strong password policies that don't match the style of password being used by the installer.
Here is a post from someone else who was having a similar issue
http://www.blackberryforums.com/deve...l-problem.html