Windows error and unwanted popups

Hey guys,


I have a few issues here. Firstly, i have the classic 'windows explorer has stopped working' when i log in. Also my browser windows (i use chrome and firefox) randomly close and programs like DivX and Flash crash occasionally. I have already scanned the drive windows is installed on, and checked the memory and also done the Sfc/scannow thing in the CMD. Nothing appears to be wrong. The virus scan (mcAfee) picked up two trojans but has not done anything about them. also, 'windows had detected copyrighted files' (???) and deleted a lot of my work. This is very frustrating, but also temper mental. For example at the moment my laptop is running fine, but this morning it kept crashing. Also, something that worries me is a popup that randomly appears that takes me to www.killerjo.net. This happens at random intervals and is quite unpleasant as it is a picture of a girl with messed up face and a screaming noise.

I have no idea what may have caused any of this or if any of these problems are related to eachother. I would be very grateful if anyone could give me some potential solutions or advice on this. Thanks.