Thank you for your reply,
There have been no previous infections found.
The computer is scanned at least once a day. It had a full format and reload near the end of August this year.
Avast has been updated since the first post. The files are still showing as win32:malware-gen when scanned in the chest. Definitions version 111001-1
To try find what this might be I did a web search for:- file size 107056 malware 12/05/2009
There were two results, both from a .fr domain. The text of the first search result says:-
"EXE Base Size Version Path 0x01000000 0x100000 6.00.2900.5512 C:\WINDOWS\Explorer. .... 1.50.0001.0000 C:\Program Files\Malwarebytes' Anti-Malware\mbamext.dll ...... Files\Alwil Software\Avast5\aswRegSvr64.exe 12/05/2009 19:31 | 107056 .."
I followed this with a web search for:- aswRegSvr64.exe 107056
Some of the text from the results:-
"5\aswRegSvr.exe 22016 bytes executable File Q:\Avast 5\aswRegSvr64.exe 46128 bytes executable File Q:\Avast 5\aswRunDll.exe 107056 bytes executable File"
"19/03/2010 20:10 22 016 aswRegSvr.exe 19/03/2010 20:10 46 128 aswRegSvr64.exe 12/05/2009 17:31 107 056 aswRunDll.exe .."
"... and Settings\maublanc\Mes documents\Téléchargements\SweetImSetup(4).exe ...... Files\Alwil Software\Avast5\aswRegSvr64.exe 12/05/2009 18:31 | 107056 "
I know it might be a coincidence that there are Avast5 files mentioned in these search results along with the same file size (107056) and dates of the system restore files Avast found in scans today. The files avast found in the scans were last modified at 16:31 and 18:31 on the date 12/05/2009, and these web search results mention the time 17:31 on the same day.
It could be that this issue is related to other issues where Avast files seem to be found as false positives.
The computer did have Avast5 on it at first, it was updated to Avast 6. If these are Avast files, this could explain why the files are only in system restore.
Are the bits of information correct?
Were there files in Avast 5 called either aswRegSvr64.exe or aswRunDll.exe that had a file size of 107056 and was last changed on 12/05/2009 ?
(Not sure if this date is UK or US way round)
Many Thanks.