Ah. Vista get's a bad rap sometimes. I actually liked Vista for business applications, but for gaming, it can cause problems. I agree with your decision to reinstall... I suggest you uninstall everything, then before you put Dragon Age back on your computer, run a Disk Cleanup on your hard drive. You can do this by going into Explorer, selecting "C" drive, and right clicking on it. Select "Properties" and on the General tab, you'll see an option for Disk Cleanup. Go into it and put a checkmark by everything-- Vista tends to accumulate a lot of junk over time.
Once you're ready to reinstall Dragon Age, do it. If you have the Awakening expansion, do that too. Install the 1.04 Patch BEFORE you start the game.
It can be found here:
http://social.biowar...page/da-patches
Good luck!