Spyware removal is a very tricky business. Once spyware gets into your system, it will be very hard to blast those spyware. You might need specific spyware removal tools. While some spyware can be fixed by your anti-spyware software, others are much more difficult to disinfect specially if they got installed before the anti-spyware software. In such cases, you might need a spyware removal tool for that particular spyware.
Smitfraud and Vundo, for instance, are spyware which are very difficult—if not impossible—to clean using conventional means. You have to use a specialized spyware removal tool for each. And if you’re unlucky enough, you might even have to do a manual spyware removal of these spyware. Those who are not familiar with spyware removal—much less, manual spyware removal—are normally instructed to download and install HijackThis. HijackThis is not a spyware removal tool but an enumerator. HJT is then run and the resulting HJT log is sent to forums specializing on spyware removal where a human will read the log, give instructions, and ask for a fresh log. This cycle goes on until the spyware is finally removed.
So, the next time you download free movies that ask you to install some codecs before you could watch, think of how pleasant spyware removal can be.