The answer to this question depends on which type of spyware or malware your PC has been attacked by. Recently, a variant of the Vundo trojan blocked me from installing Malwarebytes and that never happened before. So, I remember reading on Technibble an article about another spyware removal tool called SuperAntispyware. I installed this new tool and immediately, it detected the Vundo variant plus about 200 other issues. SuperAntiSpyware is free to install and use and is now being added to my personal tool list for spyware and malware removal. Of course, the free version does not auto-protect the computer so you would need to purchase the Professional addition to enable that support. But from all of the reviews on Technibble, it is definitely worth it.
Here is a link to download either version: SuperAntiSpyware