Very frequently on my computer, an unknown to me and unwelcome (something) opens up Microsoft Media Player and begins to play a short inane video. I close the Media Player, but within perhaps 5 minutes, the video begins again. It starts with a cartoon clapperboard, labeled "More Productions" and proceeds to 4 dopey guys trying to act and whatever. This has been afflicting my computer for perhaps a month. I tried using PANDA virus checker, but it found nothing. Could someone please tell me what has infected my computer and where to look for it and how to delete it?
Please help.
I didn't find the right solution from the Internet.