1. Many programs (usually security based ones) password protect their files for legitimate reasons such as AdAware and Spybot Search & Destroy, there are others (and avast doesn't know the password or have any way of using it even if it did know it).
When you run scans with the above programs and you delete harmful entries that they detect, a copy is kept (in quarantine/restore/backup) in case you need to reverse what you did. These are usually password protected, you should do some housekeeping and delete old backup/recovery/quarantine entries (older than two weeks or so), this will reduce the numbers of files that can't be scanned.
By examining 1) the reason given by avast! for not being able to scan the files, 2) the location of the files, you can get an idea of what program they relate to.
Files that can't be scanned are just that, not an indication they are suspicious/infected, just unable to be scanned.
2. You have no doubt inadvertently installed some form of malware.
Also useful as a diagnostic tool - Download
HiJackThis.zip - HJT Information
HiJackThis Tutorial 1 or
HiJackThis Tutorial 2For an on-line analysis -
HiJackThis Log file - On-line AnalysisIgnore any 023 reference to avast processes, this is a hiccup in the HJT 1.99.1 (especially missing file entry for avast), if you need any help with any of the analysis let us know.
OR
HiJackThis Log file - On-line Analysis 2If you haven't already got this software (freeware), download, install, update and run it.
1.
Ad-Aware2.
Spybot Search and Destroy3.
Spywareblaster Don't install this until you are clean.
4.
Ewido Security Suite