If it's the BSOD, then it could be caused by any number of things. Google the error that you get (above the line that says "If this is the first time you have seen this message...") and hopefully you'll be able to find someone in the same situation.
Here's something you can try, it can't hurt. When booting keep hitting the F8 key to get into the Safe Mode section and select "most recent good configuration" or something to that effect. If that doesn't work it may also be caused by something you installed recently causing a conflict with drivers which in turn takes forever to load so try removing anything you installed recently to see if you can uncover the culprit.