If you're using Windows, restore your files back to a point before you downloaded this piece of crap, and it should hopefully sort things out for you.
Also, run your virus/spyware scans
Also, never ever EVER EVER download video player software you're not familiar with, or that isn't known. What was the prog called?
Edit: when did you download itunes? It seems like the system has restored to a point before you had the prog. Just d/l it again I'd say.
What else doesn't work? Chances are there are dll files or updates that are required, were downloaded but since your restore are no longer seen. They probably need to be downloaded too.
Make sure you go through the registry and remove all references to this rogue program...