Where to submit a suspected trojan or virus?

[Scenobro <scenobro () tiscali it>]

I  found an explorer.exe in my system32 folder which I believe take 
precedence over the real explorer.exe located in c:\windows.
It's a 92K file that seems to be a visual basic program. Among the 
strings contained in it there is a "C:\TestDL.exe" which I didn't find 
on my disk and a url "http://www.getupdate.com/TestDownload.exe"; which 
does't exists. (the home page of that site is a textfile containing only 
"SB2").
I sent the file to virustotal.com and they found nothing.
Where I can send this file for analysis?

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