Windows explorer restarts everytime I open the downloads folder in My Documents, I have some video files in it.
I have run virus checks but nothing has been found, also moved the files to another folder but it still happens.
First turn off the thumbnail generation, then reinstall your video codec. Some of the videos are either incomplete or corrupt, causing the crash. Then try re-enabling the thumbnail generation and reopen the folder. While installing the codec, you can also choose to simply not generate the thumbnail at all.