"itunes needs reinstalling"

I have Windows 8 and I just had to restart my computer to do a few updates. iTunes was literally working find just before my computer restarted and it asked me to download and install an update, which I said to do which is why my computer restarted. Now when I click on iTunes I get 2 messages. The first says: "iTunes.exe - system error The program can't start because MediaToolbox.dll is missing from your computer. Try reinstalling the program to fix this problem." The second says: "iTunes was not installed correctly. Please reinstall iTunes. Error 7 (Windows error 126)".

I don't even know what MediaToolbox is. I don't really want to have to reinstall iTunes because I have a lot of music on there and I don't have to time to add it all back on there.

Has anyone else had this problem? If so, have you been able to solve it?