I do a thorough scan of my C: drive about once a month. After upgrading my Vista x64 system to Avast 4.8 home it seems that Avast is scanning some folders twice. I don’t think this happened in Avast 4.7. For example, Avast 4.8 scans both C:\Users(profile)\Downloads and C:\Documents and Settings(profile)\Downloads which is scanning the same folder twice ?? I stumbled across this because I had some ad ware in my downloads folder that I had excluded from scanning by using the C:\Users naming format. When I upgraded to 4.8 I had to add the C:\Documents and Settings\ naming format as an exclusion also. To circumvent this I have added the entire folder C:\Documents and Settings\ to my exclusion list so that only the C:\Users folders are scanned. This problem happens in both Avast 4.8.1169 and 4.8.1195
How exactly do you start the scan?
Right click the Avast icon, start Avast anti virus, select area to scan , folders, click on C: drive
Twice or repeated scanning shows that the user selected both Local disks and Folder selection and marked all the local disks (by their letters) again.
No Tech you are wrong…I started the scan just as I explained it, not as you assumed . This did not happen in Avast 4.7.
Mysteries… uh?
I can’t imagine why the double scanning is happening. But, remember, Vista uses circular links to %Program Files% and %Users% folders.
Avast is just reporting it. You can uncheck the options for reporting soft and hard errors on the avast settings.
It was a problem, already solved (http://forum.avast.com/index.php?topic=27330.msg223192#msg223192). Now, the only thing that rests is the reporting.
The point I am trying to make is that when doing a thorough scan of a Vista volume with Avast 4.8 , there are double scans being done of all files in the C:\Users folder. One scan via the normal C:\Users path and another scan via the Vista junction point C:\Documents and Settings. This junction point is not a true folder but just a pointer to the C:\Users folder for purposes of backwards compatability. This double scanning did not happen when using Avast 4.7.
In order to provide further proof , I went back to Avast 4.7.1098 using the instructions posted in http://forum.avast.com/index.php?topic=35471.msg298246#msg298246. The Avast report statistics were :
Avast 4.7.1098 Opened files - 415883 Tested files - 415813 Tested folders - 20892 Infected files - 5 Elapsed time - 61 min
Avast 4.8.1201 Opened files - 489717 Tested files - 489625 Tested folders - 24255 Infected files - 10 Elapsed time - 92 min
The difference in files tested and elapsed time is quite significant. Once the 4.7 scan was finished, I updated to 4.8. No other changes were made to the system. Both scans used the same VPS file version 080516-2. The infected files are all ad-ware residing in my downloads folder. Note that Avast 4.7 found 5 infections. Avast 4.8 found each file twice, hence 10 infections. There are other examples in the report file :
C:\Documents and Settings(profile)\ntuser.dat is flagged status [E] The process cannot access the file because it is being accessed by another process (32)
C:\Users(profile)\ntuser.dat is flagged status [E] The process cannot access the file because it is being accessed by another process (32)
both messages above appear in the Avast 4.8 report file. In the Avast 4.7 report, only the C:\Users message appears
The behavior will be improved in the next avast! version.
In which way?
In the way that the duplicate scanning should be reduced 
I can confirm that this happens to me on Vista also. However the problem occurs when I use Normal scan priority, as well as Thorough. I click on the standard button to scan all folders, press start, and the program scans my desktop twice, which is where all of my files are.
After the program finishes scanning my 500GB hard disk, it reports that 800GB of files were scanned. Needless to say it takes 2 hours instead of 1 hour to finish the scan, so it is very inconvenient. The problem started with 4.8. No problem with 4.7 on Vista.
David
I certainly doubt the difference would be that big (2 hours vs 1) - the “Users” folder is only one of many, so the scan time wouldn’t double (unless you install all your stuff into the Users folder).
And regarding the scan size - it doesn’t mean anything; avast! counts the size of files in archives (which might be just a Word/Excel document whose parts are extracted), so it’s pretty normal that a bigger size is reported in the final statistics than there “is” on the disk, without having to scan any part twice.