Runtime error 216--possible trojan infection?

I am running Windows 7 Pro. In trying to open any video file with any software (Zoom Player, VLC, Media Player Classic, Windows Media Player, Quicktime Player), I receive the following messages, in order:
1. "Access violation at address 77BA32CD in module ntdll.dll. Read of address 06F480C0"
2. "The instruction at 0x77ba332f referenced memory at 0x00000004. The memory could not be read."
3. "Runtime error 216 at 77BA332F"

On other forums, I have read that this problem may be caused by an infection by a Trojan called SubSeven. I've scanned the machine with Malwarebytes, Super Anti Spyware and AVG. If SubSeven is there, none of these programs found it or any other trojan (there were plenty of tracking cookies that I deleted) . The problem is still there--same error messages. This has happened so far with video files only.

Another issue with video files (I have no idea if they are connected): If I open one particular folder with video files in it, Windows Explorer immediately crashes.

I would be so grateful for any help you could offer.

Posting about the same issue across multiple forums is frowned upon because:

a) It can tie up the time that people freely give to help others working on the same problem
b) There can be contradictory instructions that could make things worse.

As you are already being helped by me here this thread is no longer open for help. Please don't do it!