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A software that will help you manage two antivirus softwares together is HandyBits VirusScan Integrator that is available as freeware from http://www.handybits.com/vsi.htm
I would also recommend AntiVir Personal Edition which again is free. You should find it at Free AntiVir . I've used this one twice too over the last 4 years and it worked great.
One of my favorites is AVG Anti-Virus by Grisoft. Their website is www.grisoft.com. As a noncommercial home user, you can download the free version which can be found in AVG Products>>AVG Free Edition. The following link should take you directly to the website of the free version: Free grisoft
A good way to test if an antivirus software is working is to do the Eicar Test. Go to http://www.eicar.org/anti_virus_test_file.htm to learn more. Read the instructions before trying it.
Disclaimer: This blog reflects my personal views only. Content does not represent the views of my employer, Info-Tech Research Group.