I have been googling this issue for a long time, and no full solutions seem to be out there. For certain mkv files, windows hangs when moving, copying, or deleting. These files play fine in a player such as GOM player. System: a fast windows 7, 64 bit box. Results: CPU change is negligible Memory usage rockets up to ~100% In cased of delete or move, "discovering files" dialogue box stays up for a long time Rename simply shows spinning icon until it finishes Action is completed after EXTREMELY long amount of time Memory usage does not return to normal "Fixes:" Disable thumbnail creation (helps for some cases) After move/rename/delete kill explorer with taskmanager, and relaunch to re-claim your memory Even with the thumbnails turned off, the issue persists. I have also tried re-muxing a file, which worked fine, but still resulted in a file with the same above issues.