First, it is malware, not a trojan virus.
Initially I would say get
Trend Micro's HijackThis! and try removing it with this software, otherwise:
Step one: Delete the Contravirus folder out of program files.
Step two: goto start...run.... type "regedit" click OK. When the registry editor pops up, Press CTRL+F the find window pops up. type in contra and click find next. Delete any entries you find by clicking on them and pressing the delete key.
Step Three: Start...run.... type in msconfig.... click on services and startup tabs in turn, and uncheck any entries you see related to Contra.
Be careful with editing the registry. It can cause system crashes. I recommend backing it up.
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