I have never tried to infect a windows computer with a mac file, but since you are kinda sure that this is the problem, and I'm kinda sure it is with this file since I don't think MS would know how to "uninstall it" per say, so now, you have to clean up your registry.
First uninstall quicktime alternative. Then delete it from your program files folder anything that say quicktime alternative, or quicktime itself. Look in the common files folder, and check out the shared folder in there also. Delete all short cuts that were left behind after the uninstall.
Restart the computer. Download this program.
TuneUp Utilities 2006 It comes with a host of cleaning and optimizing programs. The ones I wanted you to use are the registry ones. First a clean. Then search the registry for any mention of quicktime and delete it. Then defrag the registry.
Ofcouse this goes without being said. You should backup it up before tampering, but for your piece of mind, I haven't had any ill side affects from doing the above actions, and I've done this a number of times. Granted, not on the same computer. If you don't feel up to picking out quicktime from the registry by hand then you can skip that part.
The programs makes back ups anyway, so if anything goes does wrong, you can use their rescue function.
After defraging you will have to restart, it will tell you so. Restart, wait for it to talk to you again, and just to humor me, install the newest version of the Quicktime. Normal, from Apple quicktime. See if it works. If it does, then you are free to uninstall it, restart, and reinstall the window's version of quicktime alternative.