Does your computer blue screen, when trying to use your camera? If it does, it sounds as if your camera drivers arn't right. Uninstall your camera and reinstall it, get the latest drivers from the cameras web site.
Deleting your video file, start windows in safe mode, (press F8) when booting computer just before winxp startup screen. Once in safe mode you should be able to delete it.
hope this works for you.