Hi Derek, I installed ACE codec pack and that did the trick. However, a number of things have now happened to my pc. I use Serif MoviePlus 5 as my video editor. I cant get it to load a project. If I uninstall the ACE then Movisplus works. Secondly I keep getting this error message : vs filter incorrect file vresion. Any ideas what this might be about? It pops up every 2 or three minutes. I tried to uninstall ACE and reinstall it, but get the same problem.