Try running Avast in Safe Mode. Reboot into safe mode:Restart the computer
Immediately begin tapping the key.
Use the arrow keys to highlight Safe Mode and press the key.
If that doesn't work try doing a BitDefender Online Scanner:BitDefender Online Scan
For this to work you have to go to the site with IE.
If this doesn't work then I suggest posting a HijackThis log in the HJT Logs and Analysis Forum. Here is a link to that Forum: HJT Forum
Please follow the preparation directions and try not to alter your system until you receive help from one of our HJT Team Members. The preparation directions are found at the following link:Prep Guide for Posting HJT LogsPlease note: Do not try to fix any problems with HJT yourself. This is an advanced tool and requires expert analysis.