The DNS flushing suggestion is a good one.
Another possibility, what may be happening to Alan is possibly a virus/trojan has infected his computer. What it is doing is re-routing Internet requests to wherever the virus/trojan wants to take his computer. If possible, it may be helpful to do a go-back on the system, restore it to an earlier state. If the problem started two weeks ago, then try restoring the computer to an earlier state at least one to two months ago. Here is how to restore a computer, starting by clicking the START button: START > PROGRAMS > ACCESSORIES > SYSTEM TOOLS > SYSTEM RESTORE
After you have restored your computer to an earlier state, or even if the computer failed to restore it, the next step is visiting the Microsoft website and downloading the [url=https://www.microsoft.com/downloads/en/details.aspx?FamilyId=AD724AE0-E72D-4F54-9AB3-75B8EB148356&displaylang=en#SystemRequirements]Malicious Software Removal Tool[/url]. After you run that tool, I suggest you head over to Download.com [url=https://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html]here to download MalwareBytes Anti-Malware utility[/url]. This is a highly rated anti malware utility that is also free.
If you can't access and run the above anti virus softwares, and your computer failed to restore to an earlier state, then you may have to remove your hard drive and install a new one with a fresh install of Windows. Most people simply reinstall Windows on the old hard drive but you will lose all of your files. It's better to remove the old hard drive and place it in an external hard drive enclosure. Once the new hard drive is installed in the old computer you can attach the old hard drive and scan it with an anti-virus. Then you can pull your important files from the computer.
If you are ok with opening your computer and removing the hard drive (HDD) and placing it inside the external hard drive, then [url=https://www.newegg.com/Product/Product.aspx?Item=N82E16817182155]try this model of external hard drive[/url]. This model is fine as well if you're taking it to a shop to have someone else do it.
[url=https://www.newegg.com/Product/Product.aspx?Item=N82E16817182221]This model is a hot swappable model[/url] that requires no screwdrivers. Just drop the hard drive in and plug it into your computer. That's it.
I had something similar infect my computer last year, It kept my computer from accessing all antivirus websites, and disabled all three antivirus softwares on my computer. I had to buy a brand new hard drive and load up a fresh copy of Windows. I stuck the old hard drive in an external hard drive enclosure and disinfected it there. I then pulled my important files from that external hard drive and put it on my fresh install. Hopefully you won't have to go to that extreme. The virus came from a USB memory stick that came infected out of the package.
CCleaner has been around for a long time and is highly rated. Everyone should have a copy.
Revo Unistaller is a great utility that is very thorough for getting rid of things. It has been tested and rated highly by PC Magazine. If you are active about maintaining your computer, this is a free utility you should have. It can be [url=https://download.cnet.com/Revo-Uninstaller/3000-2096_4-10687648.html]downloaded here[/url].