Best bet is to download a free antivirus like AVG or Avast and an anti malware product like SuperAntispyware or MalwareBytes.
If the virus blocks those you may have to remove the drive and attach it to a computer which already has antivirus/malware tools already installed.
Personally I would also get a program like EasyCleaner (free) which can spot unnecessary files and what's running -- either may throw up a clue as to what's driving the virus.
Also look out for error messages, especially when you are disconnected from the internet and the virus tries to dial out -- often the error messages mention files that can't run or are missing.
Google those filenames and you may find a link to a specific solution to that virus.