when I start up unity it goes white and stops responding. im on vista. Help
Possibly, you have an endless loop in a script that's executed in the editor. When Unity stops responding, endless loops (or recursions) are kind of the most likely cause. One way to "debug" that kind of issue is making a copy of your project and removing all scripts in that copy. Then, start Unity and open that project. If Unity automatically starts your last opened project, use alt+click to get the project dialog (not sure, might also be ctrl or cmd depending on the platform ... I can never remember, so you'd have to try all 3 ;-) ).
If you project starts without the scripts, there's a good chance that it's an endless loop and you can start tracking it down ("which script causes Unity to stop responding").
This just happened to me and I finally figured out it was due to a While loop in a Start function whose condition was never met.