[Schnabel]

Even though what Alexa said is true, the real problem is Vista. Sadly Apple has been having troubles with Vista and compatibility. You may try seeing if there are any updates that address an issue related to this problem. You may also try to find a different version of iTunes, then have it update itself. The last thing i can recommend is to try installing Quick Time by itself, then try to install iTunes by itself and then see which program is actually causing the problem.