For the last three days I have had a problem! Today I thought I would try to sort it out! After spending five hours trying to find why I could not open any video files without getting an error message and searching umpteen sites I found a mention on MicroSoft of it being caused by a codec error. Problem is they did not tell you how to repair it! I knew about a free codec pack that I have used before, installed it and it completely solved the problem. I thought someone else might like to have that info in future so I joined and posted the information as a reply to a message on this board posted by a member who had the same problem. I hope it helps.