Many antivirus packages will automatically attempt to remove rival products as you're installing them. This process typically happens as part of the installation of a new security suite, though this isn't always the case. 

If you need to manually remove an older package, the simplest way is via the Start button, at the bottom left corner of Windows 7 and older. 

Click Control Panel (or search for this within the Start menu) then, under Programs, click uninstall a program and locate the software you want to remove from the list. Select the program, and then hit Uninstall in the toolbar above.

WARNING: If you uninstall your PC’s defences to install another but don't install another one immediately, you will be left unprotected.

Licence renewal for anti-virus packages

Many AV software packages come with a time limit attached, and need to be renewed – for a payment – each year. New PCs also regularly come with only a trial version  installed, which may only last for 30 days.

If you don't renew your licence when it's due for renewal either the package will stop protecting you altogether or will no longer be able to update itself with details of the latest threats. 

Either way, you will not be fully protected. The good news, if you don't want to part with any money, is that there are plenty of free options. 

Replacing your old security tool? Read our Which? reviews of the best antivirus software.