GAH,
Well, I'm not entirely sure as I'm no virus expert. However, it's only been in the last month that virus scanners have picked it up. The program has been around for quite some time now.
There is a 'trojan free' version (modified by Tadad) available here too if you want:
http://www.mympxplayer.org/dload.php...le&file_id=327.
Hope that helps.