Why pay for a commercial solution when many suitable free options exist?
I use Windows Defender for my real-time protection and Ad-Aware for my on-demand scanning.
In my opinion (and an opinion is all that it is) a real-time protection program is a must. Having an on-demand scanner is just an added bonus. Scan your computer with it once in a while to see if any crap has surreptitiously bypassed your real-time protection.
There are other viable options . . . and they don’t cost a cent either.
Spybot – Search & Destroy
An effective on-demand scanner.
Spyware Doctor Starter Edition
A free anti-spyware program bundled with Google Pack (I don’t recommend Google Pack – ’tis somewhat intrusive and often contains outdated versions of software). Additionally, Spyware Doctor consumes a lot of system resources, so I don’t recommend it for older computers. This program has limited real-time monitoring options and can also be used as an on-demand scanner.
AVG Anti-Spyware Free Edition
This on-demand scanner costs nothing and removes spyware others aren’t capable of removing. Real-time protection exists on the commercial version only. This program works well in combination with a program that provides real-time monitoring services.
Spyware Terminator
This program provides real-time protection as well as on-demand scans. Like other programs of this ilk, it also consumes a fair amount of system resources, so if you possess an older machine, this program may slow it down.
Spywareblaster
Providing a different style of protection, this program “blocks installation of ActiveX-based spyware, adware, browser hijackers, dialers, and other potentially unwanted software.” It doesn’t have to be running in the background like other programs. This program works well for those still using Internet Explorer.
My Recommendation
On my computer I run Windows Defender as my real-time monitor and Ad-aware as my on-demand scanner. I really think, though, that AVG Anti-Spyware does a better job removing malicious spyware and adware than any other free program out there; I’ve just been too lazy to install it on my computer. If you do install it, I’d immediately disable the real-time monitoring, automatic updates and scheduled scans as they run out anyway in thirty days. I’d then use msconfig to take it out of my startup items. Then, I’d run it manually (download updates and run a scan) about once a week.
If you have an older computer, Windows Defender might slow it down a bit. Spyware Terminator might be a better option for you. Additionally, if you have Vista installed on your computer, you already have Windows Defender so you don’t really have to worry about it. I know some of you are really anti-Microsoft, but in my opinion, Windows Defender is the obvious choice for a free real-time spyware monitor. It just works.