Did this detect a real virus or is it fake?

It can possibly act as a scam MSE. I suggest running an Avira scan. I would also recommend adblock and see if it pop-ups again.

Then install the real MSE, because it works pretty well, especially for being a Microsoft product. I was as surprised as you.

If I open up a new tab and paste the url, the same thing pops up. It's just a blank white page with the message in the middle. And it's not from the MS website.

Yea, I wouldn't suggest going into any advertised pop-ups. Unless, you know it is a safe website.

then don't go to that website LOL. they are clearly up to something illegal

Just finished scans with both Avira and Malwarebytes and nothing came up so I'm good. I guess it was just some kind of pop up ad to trick people.

Be careful with those never click them which I am guessing you already know not to do  

Ok this is just bizarre. I don't know if this means anything, but I was installing Max Payne 3 on Steam when I got the pop up in the browser about the viruses. Well I cancelled the install in order to do the Scans and once the virus scans finished I went to install MP3 all over again.

Well about 20 percent through my install, Avira popped up in the corner saying it detected something. I looked at the Virus information and Avira thinks it found a Trojan. It says the Object is "MaxPayne3.exe" and the detection is "TR/Crypt.XPACK.Gen2"

Now I know Avira is widely known for false positives. (Every time I scan it gets like 40 warnings from my Witcher 2 updates) So could this be a false positive?

To my relief I found something that suggests it's a false positive.

http://forum.avira.com/wbb/index.php?page=Thread&thread...

http://forums.runicgames.com/viewtopic.php?f=24&t=19027