I am in the process of repairing a clients Win7 Home Premium SP1 PC, initial complaint "PC hangs on windows boot screen". After confirming not boot I was able to boot to safe mode and reviewed the error logs. With nothing jumping out immediately as a problem I began to suspect malware and began a run of malwarebytes which hung halfway through requiring a hard reboot.
Following hard reboot it would now not boot at all. Running a pre-startup drive scan found a faulty data HDD, removed and was able to boot only to "last known good config". Once booted I noticed three separate AV's installed and removed the free versions and rebooted. PC still was chugging along and look at running processes revealed Bit Defender AV pegging CPU at 100% with nothing apparent running. Uninstalled Bit Defender and several apps that were clearly adware that had been installed.
After another reboot began a sweep with CCleaner for good measure an app popped up an installer that force installed "Free Ride Games". After several attempts was able to uninstall using Revo, however malware not clearly suspected. Thus I downloaded Combofix and began run. It has not been stuck at "Completed step_50" for about 2 hours. I can hear (and see) continue drive activity and I am unclear if i should simply let it continue or stop Combofix and try an alternate route pending input and instructs from the talented BleepingComputer Community/Folks?!
Edited by hamluis, 18 December 2012 - 05:45 PM.
Moved from Win 7 to AV, Firewall, etc. - Hamluis.