You have a tdl4 infection in the volsnap file.. But Avast did not touch that
I will try to reset your system back to the last good boot
Download the attached fixlist.txt to the flash drive that has FRST
Run FRST and press the fix button
Reboot to normal windows
THENDownload
aswMBR.exe ( 4.1mb ) to your desktop.
Double click the aswMBR.exe to run it Click the "Scan" button to start scan
On completion of the scan click save log, save it to your desktop and post in your next reply