I downloaded the new Vista Service Pack as advised and now of course nothing works anymore. I cannot access my taskbar with the mouse anymore, it just is a one or two pixel thick grey line at the bottom of the screen, to open it i have to push the Windows button on my keyboard, and even then only the start button responds to clicks, the tabs cannot be accessed. I tried system restore to before installing the Service Pack - Problem remains. Anyone got an idea how to fix this?

Hm...I'm not sure but I think I saw something similar to your thread

Create another admin account and on this check results -if no difference make Repair Install For Vista