Hello! Fairly new user here. I’ll try to be as detailed as possible 
Problem:
I am experiencing “SOME FILES COULD NOT BE SCANNED” post-scan. The scan results page then lists quite a few directories that I would assume are quite important to scan, with the following text in the Status field: “Error: The device is not ready (21)”.
Avast Version:
avast! FREE ANTIVIRUS 7.0.1426
Operating System:
Windows 7 Home Premium 64-bit, Service Pack 1
Other Programs Installed (or recently uninstalled):
Microsoft Security Essentials - Properly removed prior to Avast! installation
Windows Defender - Currently disabled
Malwarebytes - For separate scans, not currently running
CCleaner - For separate scans, not currently running
More details on the issue:
I installed and updated Avast and it’s definitions last night. I set it to do a full scan while I slept, and awoke to the results this morning. No viruses were found, however the results page lists several directories that were not scanned because the device was “not ready”.
At first I thought it may have been a permissions issue, but even the public folders are in the list.
I would like to stress that these directories are all on my C drive, and not on an external drive.
The Accounts on the machine are:
Windows 7’s hidden true admin account (not enabled on the login screen, for obvious reasons)
ADMIN - A separate administrator account that I can use when I don’t want to deal with the bells and whistles in my personal user account, admin level
USER1 - My account, admin level
USER2 - My husband’s account, basic user
PUBLIC - The public folders (not a user account, but listed in the errors)
Folders Affected By This Issue
C:\Documents and Settings
C:\Program Data\Application Data
C:\Program Data\Desktop
C:\Program Data\Documents
C:\Program Data\ Favourites
C:\Program Data\Start Menu
C:\Program Data\Templates
C:\Users\All Users
C:\Users\Default
C:\Users\Default\AppData\Local\Application Data
C:\Users\Default\AppData\Local\History
C:\Users\Default\AppData\Local\Temporary Internet Files
C:\Users\Default\Application Data
C:\Users\Default\Cookies
C:\Users\Default\Documents\My Music
C:\Users\Default\Documents\My Pictures
C:\Users\Default\Documents\My Videos
C:\Users\Default\Local Settings
C:\Users\Default\My Documents
C:\Users\Default\NetHood
C:\Users\Default\PrintHood
C:\Users\Default\Recent
C:\Users\Default\SendTo
C:\Users\Default\Start Menu
C:\Users\Default\Templates
C:\Users\Default User
C:\Users\ADMIN\AppData\Local\Application Data
C:\Users\ADMIN\AppData\Local\History
C:\Users\ADMIN\AppData\Local\Temporary Internet Files
C:\Users\ADMIN\Application Data
C:\Users\ADMIN\Cookies
C:\Users\ADMIN\Documents\My Music
C:\Users\ADMIN\Documents\My Pictures
C:\Users\ADMIN\Documents\My videos
C:\Users\ADMIN\Local Settings
C:\Users\ADMIN\My Documents
C:\Users\ADMIN\NetHood
C:\Users\ADMIN\PrintHood
C:\Users\ADMIN\Recent
C:\Users\ADMIN\SendTo
C:\Users\ADMIN\Start Menu
C:\Users\ADMIN\Templates
C:\Users\PUBLIC\My Music
C:\Users\PUBLIC\My Pictures
C:\Users\PUBLIC\My Videos
What I have tried since the error appeared
I ran Avast’s repair
(It seemed to have no effect)
I double and triple-checked…
I double and triple-checked to make sure that no other security programs were installed or running. I also made sure that MSE had been completely removed (it had).
[i]I ran a test scan on C:\Program Data[/i]
The scan ran for 6 seconds, Tested 1679 files, and 550 folders, a total of 818.4 MB, finding no infected files. However id did once again come up with “SOME FILES COULD NOT BE SCANNED”, those files being, from the previous list:
C:\Program Data\Application Data
C:\Program Data\Desktop
C:\Program Data\Documents
C:\Program Data\ Favourites
C:\Program Data\Start Menu
C:\Program Data\Templates
And so…
If there is any more data I can provide, please let me know. I’ve tried to be as thorough as possible to make things as easy as I can on you wonderful people who know more about this than I do. ;D
I’ll be away from the computer this evening, but I will bookmark this thread and check it regularly.
Thanks in advance.