I got a pop-up from MSE and when I clicked to get rid of viruses, a process called 'playing now radio' appeared. Was I fooled into installing malware? How to prevent this fake pop-up?
Yes, probably you've installed by accident some sort of malware. Microsoft's software doesn't display unusual pop-ups. In order to avoid such situations, you should install antivirus software in your system and try to reconsider your actions if any malicious pop-ups suggesting that your system is at risk will appear on your screen.
You can download antivirus software from here: http://software.informer.com/search/antivirus