I asked this very question on Yahoo Answers a while back, and I choose this as my best answer:
Best Answer - Chosen by Asker
PC guard is not good, I'm also a VirginMedia user.
Use the following, it's all free:
Use Firefox in preference to internet explorer.....much safer:
http://www.mozilla.com
Online Armor Free Firewall:
http://www.download.com/Online-Armor...dlPid=10831167
Installation Tutorial:
http://tinyurl.com/6a5j7z
Avast anti-virus better definitions, anti-spyware and anti-rootkit built in, faster and more reliable:
http://www.download.com/Avast-Home-E...dlPid=10852750
Setup Guide:
http://tinyurl.com/5lxy24
Malwarebytes Anti-Malware:
http://www.download.com/Malwarebytes...html?hhTest=1.
Download, install, update and select Full Scan.
Remove all infections that it finds after scan.
SUPERAntiSpyware Free Edition:
http://www.download.com/SUPERAntiSpy...-10523889.html
Download, install, check for updates, then select Scan your Computer, select your drive and select Perform Complete Scan
Spybot S&D:
http://www.safer-networking.org/en/download/index.html
Download, install, update and Immunize, turn off Tea Timer then click 'Check for problems' then when complete select all and then 'Fix Checked'
Open Spybot, click on Mode, select Advanced, click on Tools then Resident and untick Resident 'Tea Timer'
Do NOT untick Resident 'SD Helper' as that is your protection.
Spyware Doctor Starter Edition - Realtime monitoring:
http://www.download.com/Spyware-Doctor-Starter-Edition/3000-8022_4-10704508.html
This is an easy to use, preconfigured application that is ready to use as soon as you install it.
It will protect against spyware, adware, spyware trojans,keyloggers and more.
A-Squared Free:
http://www.download.com/A-squared-Fr...-10262215.html
This is not a limited version but a full tool to clean your computer from Malware, Spyware, Trojans, Backdoors, Worms, Dialers and Keyloggers.
How to use:
Download, install and it will ask to check for updates, which should be allowed and will take a few minutes initially, it will then restart the program for updates to take effect. Click on Scan and ensure deep Scan is selected then click the Scan button.
Comodo BO Clean:
http://www.comodo.com/boclean/CBO_download.html
Simply download and install, follow instructions on screen.
Go here to see what it protects you against:
http://www.comodo.com/boclean/trolist.html
Web of Trust browser addon which alerts you visually to known malicious sites:
http://www.mywot.com
All of these are very low on resources and far superior to Virgin's PC Guard.
* 2 months ago
These apparantly give you everything you need to keep your pc safe, and is low on resorces.