A couple weeks ago while glancing at my firewall log I noticed that an incoming TCP packet had been intercepted.  The local port being targeted was 27374 [Sub-7 (trojan)].  I've tried running my McAfee AV (VirusScan Pro 7.0), Antivirus.com's Housecall, Ad-Aware, and Spybot S&D and they all seem to indicate my machine is clean.  I've tried doing some research on the trojan in question, but haven't been able to discover whether or not my machine is infected, or is Sub-7 simply a name always associated with that particular port? 

I've got an Inspiron 8100 with XP Home, all critical patches, connected to net via cable modem.

Thanks for any responses.