Clicking Start on Launcher crashes Windows

What the title says... twice I managed to get to the HW title page but THEN Windows crashed.
This makes no sense!
7 hours ago I was playing the game fine. Exited the game and shut down windows as I have done every night for two years I've played this game.

I have no idea what info to give you [except that I run Vista Home Premium SP2] since I've never had technical issues aside from the occasional 90k or lobby error when a lot of other people are experiencing the same things.

Help please? :(

Well gee folks. Ty so much for the suggestions :(