You'd be better off with a version of Illustrator supported by Vista. Failing that, try the usual tricks:
Right-click on the Illustrator.exe file, choose properties, click the compatibility tab, then disable Visual Themes, Desktop Composition & display scaling on high DPI machines.
Also, run in compatibility mode (you're already doing that) and delete the aiprefs file which is in, er, C : \ Users\<yourname>\AppData\Roaming\Adobe.
Adobe.com might be a better source of information.