You probably have a video codec conflict. I don't know how to fix it manually other reformating the drive and reinstalling Windows. But then I don't know very much on the subject of removing video codecs. Windows has a habit of finding removed codec drivers, when you remove them from that control panel buried in one of those icons. So I imagine you have to delete the actual files....and beats me where those files end up on the harddrive or what strange names they have.... Or where they are hidden in the registery. Anyway, I imagine it turns into a huge mess.
I just noticed on my PC, I had terrible framerates on a lot of FMV's on a few games I own...and after I had my harddrive crash, and was forced to reinstalled, everything. Those FMV play smooth, now.
Repair probably won't work, because Windows will just reinstall all the 3rd party windows programs it can find from the harddrive. Anyway...you're probably better off just living with it.
I guess you can try that remove feature inside that sound icon in Control Panel. I think it's in there.....under Hardware, should be a button called properties in there and then it throws you into a box with two tabs....the second tab allows you to remove codecs. I guess you can try removing all of them. But I really don't know what will happen when you do. I think Windows will just reinstall them as needed....maybe. I'm pretty sure that it treats them as drivers...and if that's the case, windows doesn't delete the files....it just removes it from the registery. So, if that's the case....windows will probably just reinstall the conflicting driver, and the problem will not go away.
But it's up to you.... I'm basicly guessing. (aka: talking out of my butt)