Search for and destroy spyware, malware, adware and many other nasties with these leading tools. My favourites are Lavasofts Ad-Aware Professional and Spybot search and destroy. I also like to use the free CWShredder to get rid of some of the nastier spyware components before using the others.
What is spyware?
View full internet security suites

Lavasoft Ad-Aware Professional

Ad-Aware SE Professional Edition offers you the highest level of protection from malicious software which includes browser hijackers, keyloggers, and tracking cookies. Taking advantage of Lavasoft’s Code Sequence Identification (CSI) technology, Ad-Aware is able to protect you from both known and unknown variants of these threats; and with real-time protections of Ad-Watch you can block suspicious processes from affecting your system. All this combines to make Ad-Aware a state-of-the-art anti-spyware program for the desktop environment.
Buy Lavasoft Products

CWS Shredder

CWShredder finds and destroys traces of CoolWebSearch. CoolWebSearch is a name given to a wide range of different browser hijackers. Though the code is very different between variants, they are all used to redirect users to coolwebsearch.com and other sites affiliated with its operators.
CWShredder now cleans the CWS.Cassandra variant that includes a desktop hijack as well as a browser hijack.
Download from FileHippo

Lavasoft Ad-Aware Personal (free)

Ad-Aware Personal provides advanced protection from known data-mining, aggressive advertising, Trojans, dialers, malware, browser hijackers, and tracking components. This software is downloadable free of charge.
Download from FileHippo

Spybot Search & Destroy

Spybot - Search & Destroy can detect and remove spyware of different kinds from your computer. Spyware is a relatively new kind of threat that common anti-virus applications do not yet cover. If you see new toolbars in your Internet Explorer that you didn't intentionally install, if your browser crashes, or if you browser start page has changed without your knowing, you most probably have spyware. But even if you don't see anything, you may be infected, because more and more spyware is emerging that is silently tracking your surfing behaviour to create a marketing profile of you that will be sold to advertisement companies. Spybot-S&D is free, so there's no harm in trying to see if something snooped into your computer, too.
Download from FileHippo

Microsoft Windows Defender

Microsoft Windows Defender (formally known as Windows AntiSpyware) is a security technology that helps protect Windows users from spyware and other potentially unwanted software. Known spyware on your PC can be detected and removed. This helps reduce negative effects caused by spyware, including slow PC performance, annoying pop-up ads, unwanted changes to Internet settings, and unauthorized use of your private information. Continuous protection improves Internet browsing safety by guarding more than 50 ways spyware can enter your PC.
Download from FileHippo

Hijack This

In depth tool for scanning your computer for Spyware.
HijackThis scans areas of your registry and hard drive and returns a log of items which it detects. As this tool is recommended for advanced users only, it is  recommended that you run a scan and then post your log file on a support forum, where someone will be able to suggest which entries to remove.
Download from FileHippo