Isolated Positive Findings (Trend and Avast!)

Hello,
I hope this is the right group: (vs. the "Malware and Virus Removal" forum).

In summary:
The following threat "Threat: Win32:Hostile[Wrm]" (from an unopened email message), is / are in some MozBackUp files on a Dell E520 (profiled in control panel)
(C | Documents and Settings | My Documents)
And were on:
2 flash drives:
They are not in the mail folder (C | App data | ThunderBird | Profiles -> mail)
or in the entire Thunderbird folder (C | App data ->Thunderbird)

The following is very unclear but I include it in case there are any questions:​

*** Start of Unclear Information ***​

The culprit computer is detailed in the control panel. (Dell E520, Windows XP home SP3 totally up to date).
Avast! Free version, 5.0.545 completely up to date.

Email Client: Thunderbird: version 2.0.0.24 (20100228)

Several months ago, got a suspicious email: made a new mail folder for the message and scanned it with Avast! and a mini program from Trend's Web site. Both came up negative.
I never opened the message or ran its executable file (fed ex doc.exe(?))

I deleted the message but kept the new folder.

Have been using MozBackUp and copying the back up files (*.pcv) to 2 flash drives.

Yesterday, wanted to transfer files to another PC (Dell Optiplex 780) which runs Trend Microsystems Internet Security (Full version) Program version: 16.60.3021; engine version 9.200.1008; Pattern version: 8.183.50 completely up to date
Scanned each flash drive which came up with:
"Item: TSC_GENCLEAN; type: trojan; staus: successfully removed "
7 files:
These are quarantined by Trend.

(Problem: Each instance reports differently with Trend (i.e. Virus found; Trojan and with Avast! ) The identified threats all had different names (But are in same locations etc...
Trend finds "TROJ_CHEPVIL.H" in the Thunderbird backup files on the flash drives.

After Trend "fixed" the problem, re-ran flash drives and they are clean.

Ran the "fixed by Trend" drives through Avast! on the problem PC and they are "clean ".

Full Avast! scan (5/27/11) on the problem PC is negative.

However running the backup file(s) through Avast! (e.g.file "Thunderbird 2.0.0.24 (en-US) - 2011-05-27.pcv ") finds (found) a threat. "Threat: Win32:Hostile[Wrm] "
which Avast! moved to the virus chest.
Rescanning the file (after Avast!'s fix) is clean.
I.e. right click - scan for viruses

The mail (C | App Data | Thunderbird | Profiles -> mail) and the Thunderbird program (C | App Data -> Thunderbird) are both clean according to Avast!

*** End of Unclear Information ***​

Malwarebytes is negative.

Should I move this post to the "Malware and Virus Removal" forum?
And
download the programs and run the steps outlined:
Here
"Windows BBS - Announcements in Forum : Malware and Virus Removal "
http://www.windowsbbs.com/malware-virus-removal/announcements.html

Thank you!