Computer may be infected.

[VG_addict]

Lately, I've been getting several pop up windows that say, "Warning, Your Computer May Be Infected. The system may have found two viruses that pose a serious threat: Browser.Hijacker.Spy./Trojan.FakeAV-Download". Then it gives a phone number.

I can't exit the window unless I shut down my computer, then turn it back on.

What do I do?

[VIKINGS]

Reinstall windows, install an antivirus, then do a full scan of all your drives before connecting to the internet?

[Warrior]

If you have another PC, burn a version of linux (I prefer linux mint) and you can then load up the linux desktop with no installing required, backup your files on the hard drive and then you can simply reinstall windows and if you want I can give you a list of free great protection for windows.

[Ragnar]

Reinstall windows, install an antivirus, then do a full scan of all your drives before connecting to the internet?

That's overkill, don't do that unless you're thinking last resort.

Fetch some free antivirus install while at a friends house or library or whatever, and toss it on a thumbdrive. Boot computer in safe mode, install AV, scan computer.

[VG_addict]

But I already have antivirus software.

And it only pops up when I go to site where I can watch cartoons.

Is it just another scam?

[Ragnar]

I wouldn't assume it's just a scam. If it's just some popup ad you could ctrl+alt+delete and close your browser. You may just have some virus that your current AV doesn't actively find, and it's just picking up side effects. Try some alternate antivirus software.

[Stark]

Try malwarebytes as well at some point. its a really handy free program for getting things the antivirus miss

[MaslowK]

Assuming it does actually refuse to let you close the window by any means, it does sound very reminiscent of the recent "this is the fbi/cia/whatever, pay us X cash to unlock!" scams (albeit without a ransom amount), and them posting a phone number doesn't help its case (no legitimate antivirus does this AFAIK). As others have mentioned, you'll be best off booting into safe mode to attempt to fix it before resorting to a reinstall.

Once in safe mode the first things to check are the startup items and services. To do that, go to the start menu, type msconfig into the search box and hit enter. On the Services tab, check the box at the bottom that says "Hide all Microsoft services", then disable anything that wasn't hidden. Then go to the Startup tab and click "Disable all" (99% of the time this won't affect windows ability to function), and finally hit Ok. Reboot your computer normally and see if the issue is still there.

If it is, then go download Malwarebytes, install it then run it in safe mode. Keep in mind that a lot of malware will cause damage to your system, usually by corrupting or editing particular files or configuration settings; with these, even if you remove the malware itself, it won't reverse these type of changes.

[Knightshade]

As said above MalwareBytes is probably your best bet for dealing with this I had a similar issue except the popup came up as soon as I restarted my computer as well already had MalwareBytes installed so I booted into safe mode didn't get the pop up ran both MalwareBytes and my virus scanner rebooted and problem was solved