You should definitely stick to the specific file as the use of a wildcard in the folder leaves too big a hole.
When the alert comes up, you can actually copy the actual path and file name to use in the exclusions lists.
You could also use the Program Settings, Exclusions, Add, use the browse button to actually select the file, now that should work (for the on-demand scans). You could also copy the path from the Selected paths: filed and use that in the Standard Shield, see image.
Note there are quotes around the path in the image, you could try that as the spaces in the path could be the issue in w2k. Or you could try the short path like Progra~1 style of writing folders with spaces.
You should also really confirm the detection is good/bad and have avast correct if bad, that is the right way to go about it, so it is corrected for all avast users.
You could also check the offending/suspect file at:
VirusTotal - Multi engine on-line virus scanner and
report the findings here. You can't do this with the file securely in the chest, you need to extract it to a temporary (not original) location first, see below.
Create a folder called Suspect in the C:\ drive, e.g. C:\Suspect. Now exclude that folder in the
Standard Shield, Customize, Advanced, Add, type (or copy and paste) C:\Suspect\* That will stop the standard shield scanning any file you put in that folder. You should now be able to export any file in the chest to this folder and upload it to VirusTotal without avast alerting.
If it is indeed a false positive, see
http://forum.avast.com/index.php?topic=34950.msg293451#msg293451, how to report it to avast! and what to do to exclude them until the problem is corrected.