How to remove a virus 3: download and run Malwarebytes...

As discussed above you need to use a different malware scanner to that which you have installed, since your current antivirus software hasn't detected the malware. So now we're going to use an on-demand scanner, which searches for malware infections only when you open the program manually and run a scan. The benefit here is that you can run an on-demand scanner alongside the real-time security software we discussed at the outset.
We're going to use the Malwarebytes Anti-Malware free on-demand scanner. To get started, reconnect to the web so you can download, install, and update Malwarebytes; but disconnect from the internet again before you start scanning. To be entirely safe the best process is to download Malwarebytes on another computer, save it to a USB flash drive, and take the flash drive to the infected computer.
After downloading Malwarebytes, run the setup file and follow the wizard to install the program. Once installed, Malwarebytes will check for updates and launch the app itself. If you get a message about the database being outdated, select Yes to download the updates and then click OK when prompted that they have been successfully installed.
Once the program opens, keep the default scan option ('Perform quick scan') selected and click the Scan button.
Though it offers a full-scan option, Malwarebytes recommends that you perform the quick scan first, as that scan usually finds all of the infections anyway. Depending on your computer, the quick scan can take anywhere from 5 to 20 minutes, whereas the full scan might take 30 to 60 minutes or more. While Malwarebytes is scanning, you can see how many files or objects the software has already scanned, and how many of those files it has identified either as being malware or as being infected by malware.
If Malwarebytes automatically disappears after it begins scanning and won't reopen, you probably have a rootkit or other deep infection that automatically kills scanners to prevent them from removing it. Though you can try some tricks to get around this malicious technique, you might be better off reinstalling Windows after backing up your files (as discussed later), in view of the time and effort you may have to expend to beat the malware.
If Malwarebytes' quick scan doesn't find any infections, it will show you a text file containing the scan results. If you still think that your system may have acquired some malware, consider running a full scan with Malwarebytes and trying the other scanners mentioned earlier. If Malwarebytes does find infections, it'll bring up a dialog box warning you of the discovery. To see what suspect files the scanner detected, click the Scan Results button in the lower right. It automatically selects to remove the ones that are known to be dangerous. If you want to remove other detected items, select them as well. Then click the Remove Selected button in the lower left to get rid of the specified infections.
After removing the infections, Malwarebytes will open a text file listing the scan and removal results; skim through these results to confirm that the antivirus program successfully removed each item. Malwarebytes may also prompt you to restart your PC in order to complete the removal process, which you should do.
If your problems persist after you've run the quick scan and it has found and removed unwanted files, consider running a full scan with Malwarebytes and the other scanners mentioned earlier. If the malware appears to be gone, run a full scan with your real-time antivirus program to confirm that result. Then jump to step 5. If not...

How to remove a virus 4: ...or use a virus removal device such as the FixMeStick

This step requires you to shell out some cash. But it will be worth it if Malwarebytes hasn't solved your problem. Sometimes simply going online to download software - even security software - opens up your PC or laptop to more pain. So using a bootable USB stick with pre-installed security software is a good way of scanning and cleaning your PC without going online. To create one you just have to download and install a security software package to a USB disk. (If you are reading this story and you don't have a virus problem, this wouldn't be a terrible idea.)
Trouble is: unless you are the network admin for an office, you are unlikely to have such a disk to hand.
FixMeStick
FixMeStick is an easy to use 'plug and play' antivirus USB stick. It's ideal in this scenario: perfect for anyone wanting a no fuss antivirus solution for multiple devices, without having to venture online to download and install software. It isn't cheap, however. It costs £45 per stick, but the device can at least be used on up to three PCs or Macs per year. If you find yourself regularly rescuing PCs and laptops for unsavvy friends and family, it may be worth a punt.
In essense FixMeStick is a self-bootable USB device which operates in its own clean environment, identifying viruses and malware such as spyware, Trojans, ransomware and so on. It includes security software from Sophos, Kaspersky and Vipre. Plug it in and start scanning for viruses and malware. What it finds it can clean.

How to remove a virus 5: after the event

Your PC should now be free of malware. But that may not free you from the after effects of the infection. You may find, for instance, that your web browser defaults to a weird search engine and has a home page you didn't choose. You can solve this by following the steps in our 'How to remove unwanted web browser toolbars' piece.
More importantly, you should change all your passwords, and login details for anything that contains sensitive information. Remember that this includes email and social media accounts. Visit Security Advisor.