Recently came through a really bad "patch" with my home computer.
Started running really slowly. I suspected a Key-logger.
Now I should point out that I do not frequent dodgy websites. However, having two daughters, I am no stranger to computer infections - when they were younger, and looking around for free ring-tones and the likes, my computer was forever falling-over. However, thanks to Spybot and AVG (who never seem to argue with each other) I always cleared up these problems.
So when my computer started acting up a month back I thought " here we go again".
However, I immediately realised I might be in real trouble - I found out a while back how to set up Scheduler to run Spybot. So Spybot had been checking my computer on a regular basis. So Spybot must have caught any problems I had !?
I checked for the latest updates and got them downloaded. Ran Spybot and found nothing!? My antivirus came up blank as well. Puzzled!
Then a week or so later a new symptom started - the computer would restart??
With that symptom I had a new clue and went on a trawl of the forums. I found plenty of advice telling me I had a virus and that it had crippled Windows. I struggled on for another couple of days but got fed up of the intermitent restarts.
I did not have an extended warranty. For computers, I believe they are a total waste of money (as the computer is over three years old it would probably not have been covered anyway).
I have a very friendly little computer shop that I go to for all my real IT needs. This Computer specialist has been a god-send over the years and the only time I have strayed is when I replaced my out-dated home computer (with this one).
I told him what I had and what I found out. He gave me his usual patient smile and told me to phone-back tomorow.
So what was the virus he found or the malware I was ready to blame?
Niether.
Apparently my hard drive was faulty and one of the two memory cards had failed. He said that it is easy to mistake slow running and internmitent restarts as a problem with a virus, malware or other malicious/nuisance programs. However, the clue I had given him was that Spybot and AVG had found nothing.
He said he checked all the common culprits first and it did not take him long to track it down. I had spent days and days checking software and all the time it was hardware :-/
Hard drives do not last forever and any electrical component will eventually burnout. Until someone tells you that it does not cross your mind.
A new hard-drive, some replacement memory, and a full re-instal and my computer was working as fast as the day I bought it. He gave me the old hard-drive in case there was stuff I needed that he had not recovered.
I spent the next day playing with the hard drive (in a caddy). It took a long time for me to find some clues that might have pointed to the hard drive problem that had been plaging me for weeks.
So my advice is this
If antivirus can't find it
and Spybot can't find it
Your PC needs repair.