Last night, I was downloading two files simultaneously. They finished at about the same time, and when they finished, Microsoft Security Essentials detected a Vawtrak Trojan virus and quarantined it. I immediately deleted the virus, and both files, and ran an antivirus scan on Malwarebytes. The scan didn't detect anything. However, the 'Windows Activation Technologies' pop-up (the same one in the attached image) kept appearing every two minutes or so, so I knew there was something fishy.
I shut down the computer, then restarted it in Safe Mode. I ran a full scan in Microsoft Security Essentials while in Safe Mode. It didn't detect anything. I restarted the computer in normal mode, and now the pop-up isn't appearing anymore, and everything appears normal.
However, how do I know the virus isn't running in the background undetected? Does anyone have experience with this? Thanks!