Have you got an Antivirus running on your system?
If you have:
- does it run on a schedule?
- does it update regularly?
- Is it out of Subscription?
There is no reason not to have a working antivirus installed on your PC. There is a vast array of options when it comes to Anti-Virus and one of the best free versions is Avast. It is currently the number one downloaded from Downloads.com. Avast has a "real-time" scanner, This means that any file you access on your PC gets scanned at time of opening. Not all of the free ones do this, but they have other features that maybe Avast does not. Some others have parental controls included and some have a firewall.
Other options include : BT offer within their subscription package, an Anti Virus for free, as do Sky, as do Virgin Media.
A google search for top 10 antivirus or top 10 free antivirus, will give you a raft of options and opinions.
Do make sure it is set up to run on schedule, a quick scan once a week and a full scan once a fortnight. Ensure that it is able to update automatically, as newer threats will be added frequently.
It does not matter whether you pay for it or whether its a free version make sure it updates regularly and can be set to run on a schedule automatically and that the schedule is set to run when the system is running and not at 3.00am on a Wednesday morning when it is switched off.
Antivirus will only run when the PC is switched on!