I have a pack of videos that we're ripped and encoded from old VHS tapes. The pack contains about about 50 episodes, of which 4 of them will not play in Windows Media Center, nor do they have a thumbnail in Windows Explorer (in Windows 7). They just appear as a generic icon and give me a "Windows Media Player encounter a problem while playing the file" error" error. I opened these all the files in VirtualDub and under "File Properties" I was able to get the encoding information. All the videos (both the playable and non-playable ones) are all using the same Xvid MPEG-4 / Fraunhoff IIS MPEG Layer-3 Codecs. The only difference is on the bad files, VirtualDub has the keyframes listed at 1 and gives the following error message when opening: I've already confirmed on two different HDDs that the files are not corrupt in downloading, so I'm assuming the problem has to do with the software on my end.