My preferred virus checker for my home PC is NOD32. It is very lightweight and has very little impact on software performance, especially launching applications. The performance feels much like as if there is no virus checker installed. For example, Thunderbird (with several large mailboxes) loads in about 7 seconds on my old AMD XP3000+ PC compared to 11 seconds with Avast and 14 seconds from what I recall with AVG. It can be easily disabled to speed up transfer rates when copying a large number of files, especially executables and installers. The catch however is the cost, ~€80 for 3 years for a 1 PC home user license. For those who have an older PC and plenty of RAM, but would like to give their PC another performance boost, I would suggest trying NOD32, at least the 30 day trial version.
For those who want a free virus checker, but have a fairly old system and can’t afford to upgrade the PC, Avast seems to be a little less resource hungry than AVG from my experience. Applications load a little quicker with it than AVG, at least the system’s I’ve tried it on. This virus checker likes to talk each time it applies an update or whenever it encounters an infection (reminds me of Lexmark’s printing software), however, this can be turned off. This virus checker requires annual registration, however, while there is no charge for it, it can be a bit of a hassle installing it on someone else’s PC. While Avast does lack AVG’s link scanner, the Firefox browser makes a good alternative which does a similar job and warns the user before entering a rogue or malware infected website.
Finally, for those who have a good fast system or who prefer Internet Explorer and are interested in being warned about which links are dangerous when returned in search engine results or manually entered, AVG seems to work very well for this. I also typically recommend installing AVG to those who are just learning to go online or those with children. Another thing I like about AVG is that it does not require registration, making it quick to install. Just watch out for the program download size, as it can take around 10 minutes to download on a 1Mb connection. One drawback with the AVG home edition is that it does not include anti-Rootkit protection, unlike Avast and NOD32. For those wondering if the AVG Toolbar is required to scan links, from my experience, AVG still shows which links are safe in search results even if the AVG Toolbar is not installed.
For an infection clean-up, my preferred tool is Spybot Search & Destroy. It works best when run in the Windows safe mode. Its scanning speed varies a lot depending on the performance of a PC, varying between 15 minutes to over an hour from my experience (using version 1.6). For more advanced users who are familiar with start up processes and know how to check what start-up processes and applications are legitimate or not, a combination of HiJackThis and a BartPE boot CD is difficult to beat when dealing with stubborn Malware DLL files.
So far, I have heard more complaints with Norton and McAfee than any other virus checker. Both are very heavy on system resources, especially a combination of Norton Internet Security and Windows Vista. For example, I’ve seen someone with a fairly decent laptop (Core 2 Duo 1.6GHz with 2GB RAM), running Windows Vista Home Premium and Norton Internet Security and it took 5 minutes from powering on the system to the time I could bring up the browser and homepage (Google).
Once Norton was taken off and replaced with AVG Free edition, it reduced the boot time to under 2 minutes and the system was noticeably more responsive.
Avira 
Linear Mode
