Here is a free and very good antivirus tool called avg free,
Note; You should never use more than one antivirus on your computer at a time,
http://free.grisoft.com/doc/downloads-products/us/frt/0?prd=aff
The free edition of spyware doctor, The best for removing spyware and malware and its free,
http://www.download.com/Spyware-Doctor-Starter-Edition/3000-8022_4-10754824.html
Advanced Windows Care;
This tool is an optimizer with a registry cleaner and imunization tool against infections from the internet,
http://www.download.com/Advanced-WindowsCare-Personal/3000-2086-10407614.html
Here is the adaware se free personal and is a very good spyware removal tool
http://www.download.com/3000-2144-10045910.html
Here is an antispyware software called avg free antispyware,
http://free.grisoft.com/doc/downloads-products/us/frt/0?prd=asf
SG