Dudley wrote:
Videolan. Videolan is your friend.
Wouldn't have helped here, I've seen this before. The file Malc downloaded would actually be corrupted on purpose, and have a text file that says "you need XYZ codec to watch this, you can download it from blah". Videolan won't work because XYZ codec doesn't exist, see. I've seen variants of this where the supposed video file is compressed in an archive with some special unarchiver program which (of course) turns out to be trojan.
Malc -- be careful if you don't uninstall Windows. I had a PC get trojaned under me once; not sure how. I didn't find out for ages afterward when I got a bollocking from my ISP for sending spam; I ran a check on the PC and it had active SMTP connections to half the internet. The machine looked fine though, and had passed a (clearly bollocks) virus scan of some description.
Top tip -- if you can play them back, get HD 720p MKV rips of TV programs. The scammers don't seem to bother with them (fewer downloaders and more bandwidth needed). I've yet to see any fakes or scams downloading those.