File extensions changing automatically

Hello all,

I have a 320 GB external Hard drive from Iomega. Off late, I can see most of my avi, MPG and mp3 files changing on its own to JPg files!

I thought it to be a problem with the laptop I have ( probably a virus). I then plugged it into my new desktop which had an updated antivirus in it and I then scanned the hard drive for infections. It cleaned a lot of W32 sally virus (wonder what that is). After scanning, I had hopes that the problem would have sorted out but to my dismay, things havent changed.

I can do " Open with" and open the video or audio files with media player, but why are they changing into Jpeg files????

And if i Change the file extensions, they revert back to its original form, only to change back into JPG later

PLEASE HELP SOMEONE....

 

Thanks a ton Kestrel.... I could have messed up my External hard drive with Combofix!!!!