dsr.xvid-sys a virus or Trojan ?

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 Now in dozens of xvid files & several bit torrents I see this "dsr.xvid-sys
What exactly is the dsr. or sys extension for in a xvid file ?
I read that dsr can be a visual basic command .
My concern is that someone may be sneaking a virus or trojan by .
I just recently cleaned up my computer from a trojan that did wonders for
making spambots ,didn't make my ISP to happy either .
Video files & stuff like Youtube is expected to be targeted for trojan
infection if this hasn't happened already .
Sorry if this seems like a stupid question but I'm trying to learn &
practice safety in my use of the internet .
Thanks for any advice :)

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