There are a several free security products around.
Firewall : Comodo (which now comes with their anti-virus program built in) is available
here. It can be a bit intrusive to start with though, asking you to confirm what is and isn't allowed to access the net. Zone Alarm Free is available
here. There are others around, but some of them aren't very friendly to use.
Anti-virus : Avira, available
here, AVG Free which is available
here, Avast! which is available
here .
Anti-malware : Lavasoft AdAware, Malwarebytes Anti-Malware, Spybot Search and Destroy, Superantispyware all have free versions
If you are with Virgin, their PC Guard suite is available free for people using their broadband L and above packages (that's the 10/20/50MB packages). It may be worth checking if your ISP offers something similar.