My young son called me into his room last night to show me a pop-up window on his computer.

The window showed a bill from a company called microbillsys.com, and it was asking for £39.99 for a subscription service it said my son had subscribed to. The website is pornographic. Can this company demand money from a 12-year-old for a porn site?

Alan Trueick

Your son’s computer has been infected with a virus. This causes the pop-up and you don’t owe the company money, nor is it possible for the company to get the money from you without you knowing. Getting rid of the virus will take a few steps. Make sure your virus scanner and anti-spyware program are up to date.

You should download and install the AVG Anti-Rootkit program but do not run it yet. Restart the computer in Safe Mode. To do this, reboot and when the black screen appears, start slowly tapping the F8 key on the keyboard. After a while a Boot Menu will appear. Select Safe Mode using the arrow keys and press Enter.

Once it has started in Safe Mode, run a full scan using the anti-spyware, then the anti-virus program, then the AVG anti-rootkit. This should detect and remove the offending virus. Once all the scans have been completed you can reboot the computer into its normal mode. You then need to clean the System Restore tool.

Follow this advice. You need to follow the instructions under ‘Disabling system restore’, then those marked ‘Enabling system restore’, and finally create a new restore point by following the instructions under ‘Manually creating restore points’. To avoid getting re-infected, make sure you have a full firewall running on all your computers.