Fairly new too the site, I've been lurking over the past week reading up on topics trying to self-fix but I'm starting to run out of ideas and could do with a little guidance.
Around 4 or 5 days ago I updated Avast & Zonealarm at the same time on Windows 7. As with most updates, it makes you restart once the installation has completed. When the computer restarted, no programs would execute, the wireless signal was persistently on the busy (little blue circle next to the bars) and every time I tried loading Avast or Zonealarm, they just would sit there doing nothing. During this instance I tried doing various restarts just to see if Windows hadn't loaded properly which sometimes happens on my laptop. I left this overnight just to see if the laptop was having a funny turn.
When I came back it essentially hadn't moved over night, so I knew something was up. I managed to get into Safe mode and ran RKill but RKill is finding no issues. Super Anti-Spyware had found 4 trojans and cleaned them up. CC Cleaner did its thing fine. I then tried to reload in normal mode to see if everything had gone swimmingly. No luck though, I managed to get Avast & Zonealarm up and running but an attempt at a full scan with Avast caused the computer to restart when it noticed Explorer was acting suspiciously. So I went back into Safe mode, ran RKill, Super Anti-Spyware and CC Cleaner again but they are all coming up clean again. At this point I'd ran out of time and had come back here to lurk to see if I could find something else to help. I read that TDSSKiller was probably my best bet.
Went back to the Laptop and tried TDSSKiller in safe mode with networking, it didn't install properly first time (Froze at 80%) but a second attempt in normal Safe Mode and it finds no threats. I tried an overnight scan in safe mode with Avast and it got too a certain point and has been stuck there since.
Also I've tried a system restore but it fails each time, first time around it said because Avast was active it wouldn't be able to restore, I disabled that and tried again but still no luck.
My next thought it attempting this solution http://www.bleepingcomputer.com/forums/topic452209.html
but I don't get the FakeHDD error when I boot.
Sorry if this is a bit short on specifics, it's been a frustrating few days and I've tried so much it's hard to remember error codes.
EDIT - Have used Malwarebytes a couple of times and this seems to have problem scanning too. Often freezes.