So today we are going to see about this free software that is an anti-spyware called SpyBot- Search & Destroy(v 1.5 1.19.) Another free anti-spyware is Lavasoft's Ad-Aware SE Free edition (Information/Download )However it uses way too much system resources and is sluggish.But it does more than a decent job of scanning and removing spywares.
One of the best free tools around, it is ranked in the top ten in download.com's most popular software.
Installation of the software is a breeze. On startup we can see four buttons to the left-Search&Destroy, Recovery ,Immunize & Update. On pressing the Search & Destroy tab the software begins to scan the system. Unlike other antispyware software, Spybot-S&D does not show which file it is scanning at present. Instead it displays the spyware or adware it is searching for. The scanning can be stopped any time, but cannot be resumed. After the scan SpyBot asks you wether to repair any spyware if/when found. You can create a back-up in case you are not sure if deleting the spyware is right for your system.
If any harm has been done to your computer and if you have back-uped your system you can undo the changes using the Recovery button.
SpyBot includes an "Immunize" function, which is a long list of webpages, URLs, and domains that are dirty with spyware. If you browse, get redirected, or popped-up to one of those webpages, SpyBot will keep the webpage from loading onto your computer -- all you get is an empty browser window. Whatever you were looking for, if it gets blocked, it's your chance to get it elsewhere, less hazardously.
The Update button allows you to get the latest defination files which are released mastly once in a week.
SpyBot has another function that's worthwhile. They have "TeaTimer," which monitors your registry. If anything tries to change the registry, TeaTimer stops the change, and asks your permission to accept or deny as you see fit.Since the registry is unfathomable to most of us, it is a favorite target of spyware installations. At least, with SpyBot's TeaTimer, changes to the registry become conscious decisions instead of being performed behind your back, even if you don't exactly understand the function. Getting a TeaTimer alert by complete surprise -- such as while browsing the web -- would be a definite reason to deny the change. Getting a TeaTimer alert while changing your wallpaper would be definite reason to accept the change.
The Settings tab allows you to modify a number of settings.This can be seen only if the advanced mode is activated. You can activate it by clicking Mode>Advanced on the top of the window.
Spybot is a software that is being run by Donations and is hence a freeware. As it is not supported like Ad-Aware, which has a paid version as well it is not a software that will totally spyware-proof your PC. Hence my rating would be 7/10. If you can please donate for the owner.

Information:Officiall site
Download(9.27 mb): Mirror 1, Mirror 2, Mirror 3, Mirror 4

Note:Unlike anti-virus software that you can't run more than one at a time (such as running Norton and McAfee at the same time), it is possible and it is recommended that you run an assortment of anti-spyware at the same time, each running in the background.
Sources:http://www.adwarereport.com/