This post is a general education post to help people become more familiar with computer viruses and trojans. For those who have never seen an actual computer virus taking over a computer, or who have seen it but did not realize what happened to their computer, here is a short video showing how a virus can take over your computer (I did not make this).
A couple of things to note here. The first warning sign that there was a virus was when the web page he was trying to access did not come up, but instead there was a page for a completely different site that came up. That should have been the first warning sign. The second was that a web page, not owned by Microsoft, said that there was something wrong with his computer. This would be like having some random person on the street come up to you and say that there has been a recalled issued for your car, and then they ask for your keys. You wouldn't give them your keys, so why would you trust some random website to tell you that your computer is broken and they need to fix it.
Up to this point the computer does not have a virus, it is just the webpage telling him that there is a problem. The next thing that was wrong with was that the web page began scanning his computer. No webpage, even legitimate ones should ever scan your computer. Again, that would be like someone calling you on the phone and offering to fix your car over the phone. If someone did that then you should suggest they take a trip to the loony bin, and when a website tries to do the same thing with your computer then you should also close your browser and don't go any further. Up to this point your computer still does not have a virus, and still works just fine. But when you download the virus, and run it (some viruses might be able to run immediately when you download them) then you have problems.
If you get to the point where you have a virus on your computer, then even if it says there are other problems, and even if it offers to fix the problem (for a fee) then don't do it. Either you will have to fix the problem yourself, if you know how, or find someone you can trust, who can fix it. Also keep in mind that no trustworthy anti-virus software will ever ask you to pay a fee after downloading it randomly off the internet. If you did not purchase the software in the normal way (off of a trusted site, or in an actual store) then it is not legitimate, and your should never give them credit card information.