Its been years since I installed an anti-spyware program. Keyloggers and other nasties might have gotten installed and so I'm looking for a program to flush them out. I used to use Spybot-S&D, but I think in the past it would slow the PC down. Which free anti-spyware program do you recommend/have used extensively?
Here's a direct link to Microsoft Security Essentials:
Use Microsoft Security Essentials to guard against viruses, spyware, and other evil software. It provides real-time protection for your home or small business PCs.
Microsoft Security Essentials is free * and we designed it to be simple to install and easy to use. It runs quietly and efficiently in the background so you don't have to worry about interruptions or making updates.
Note (*): Your PC must run genuine Windows to install Microsoft Security Essentials.
First thing I do on a new install (thus making this answer slightly off-topic), is install Hijackthis and make it automatically start at every boot. The very first time, shortly after installation of the OS, I blindly acknowledge all lines.
Then after that, at every boot HijackThis is automacically started and I must be able to explain to myself new entries when they appear or take counter actions.
I have a fairly good IT background, that is the second catch in this answer, though my Windows knowledge is not much better than a just above average user. For this HijackThis to be workable, you need to be able to search the Internet when there are findings and you need to be able to estimate the value of what you've found.
The advantage is that it takes very little system resources. The disadvantage is that it requires some basic knowledge of how a computer works. Another disadvantage is that it takes time to analyse the reports, but findings are only reported every once in a blue moon to me.
Virus Bulletin an industry leader in Anti-virus/Anti-spyware comparisons has a chart that may help you out (See http://www.virusbtn.com/vb100/index, http://www.virusbtn.com/vb100/RAP/RAP-quadrant-Oct11-Apr12-large.jpg)
Based on this I would suggest that you look at something like Ad-Aware for good detection which comes in a free version (see http://www.lavasoft.com/products/ad_aware_free.php), however there are quite a few options.
Personally I have used Ad-aware and it is quite good. If easy of use is an issue you should consider using Microsoft Security Essentials, which is ideal for home use. It is easy to used and free. (See http://windows.microsoft.com/mse)
A similar question has already been asked, here's a copy/paste of one of the best answer :
No single antispyware catches everything. Different ones have different strengths. Here are a few suggestions:
For preventative, real-time protection, one of the known best is Spyware Terminator. It used to have the dark cloud of "rogue antispyware" reputation hanging over it, but that cloud has been lifted. While TechSupportAlert.com says Windows Defender's overall detection rate is slightly higher, it does plainly say that Spyware Terminator is much stronger when it comes to preventing infection in the first place.
Another product that I have found to be quite effective is CyberDefender. This is another product that was on probation at Spyware Warrior, and in fact some scanners will still detect its SpyBlocs components as adware, but Eric Howes (editor of SW) has informed me that these items are in fact legitimate.
CyberDefender is not just antispyware. It also has antivirus, anti-spam, and anti-fraud in an all-in-one "seamless" unit that is supposed to be fully compatible with an existing, conventional antivirus on your machine. But as I've posted in a few other threads, I see no need for it. I recently replaced AVG Free antivirus and Windows Defender with this product, and have no longer needed to manually scan for spyware since then.
CyberDefender's method of learning works in a way similar to that of class-leading HIPS product Novatix Cyberhawk (the clients are the threat sensors), and they've found a way to continue offering this product for free by placing unobtrusive ads in the console window, and eliminating virtually all distribution bandwidth costs by delegating updating responsibilities between peers. The client that detects a new threat gets updated first (usually within an hour, before most outbreaks are even over), which in turn uses its own local bandwidth to update a number of its peers, which in turn update more peers, and so on. This creates much less strain on a single Internet connection, allows updates to be distributed faster, and again, saves the company a lot of money.
Either of the two products I've mentioned above will protect you from most threats, but you should never assume your computer is clean just because one scanner says it is. You should also have at least one on-demand scanner on hand. The two I recommend most are AVG Anti-Spyware Free and a-squared Free. These are both competent at detecting spyware, but they were originally designed to detect malware especially (Trojans, backdoors, etc.) According to Andreas Clementi's AV-Comparatives (AT-Comparatives, in this case), these are the top two anti-Trojan scanners. They are also the only two in the competition that offer free on-demand scanners.
Hope this helps!
(note: I added links to products for better reading/searching)