quicktime help

First let me say that this problem is on a windows machine for some reason, every quicktime file from the internet just has a quicktime logo with a question mark on it. I tried going through the preferences and changing things but that didnt work. what do I do to let it go back to normal? it was just fine a week ago and I havnt changed anything or installed anything new.

EDIT: I just tried re-installing quicktime and that didnt do anything.....

 

i know this is a common problem because there are users on the apple.com forums with the same issue but hardly anyone goes there so there are no replies yet (and it could take days to get one). could someone please help?