usually on avi files, you cant preview them because (i think) the beginning and the end of the file are needed to play.

also, scanning any audio or video format isnt neccisary, but its not harmfull. viruses cannot be added to these formats since they use codecs (a type of format security sandbox that can only execute audio/video databits that is not executable on any system)

they are kind of like .txt files that only have words in them, and thus cannot be executed.

but wma/wmv files can be set to use the DRM license acquisition to have YOU install malware, viruses, spyware/adware and other nasty things onto your computer. i would recommend not downloading these types at all.. and most spam is generated with these formats. http://www.gnutellaforums.com/showth...threadid=31862