I recently had malware/virus on my Window7 pro computer. I am pretty sure it has been removed. Malwarebytes Anti-Malware no longer finds anything. And the computer is running pretty stable now. But every once in a while (I would say every couple hours) something is erasing my hosts file. I do a lot of web development. So I routinely set the host file to simulate the actual host.
The original virus was the one making it look like you had viruses and would try to hoax you into "buying" virus scanning software. But this has been removed. After this I was having issues with Internet Explorer periodically just popping up out of no where and displaying ads. I don't even use IE and instead use FireFox. I have since disabled IE. Every once in a while my browser will redirect to certain ad pages. But not often. Thought I had this nixed. But Malwarebytes not showing anything.