Hi I use Malwarebytes, Ccleaner, Asquared, Advanced System Care, all free editions and Kaspersky Internet Security (free from Barclays). I've had no bad experiences yet! I'm using Win 7 home premium 64 bit.
Free suggestions: Firewall :PCTools Anti Virus: Avira (I use this) , or MS Security Essentials. Anti Malware: Malawarebytes. SAS very good and soon to launch the free 64 bit - there is a beta version. A few eventviewer probs, so I am waiting for the final version. Also Spywareblaster works fine. CCleaner All ok with W7 64 bit, but you only want to run one anti virus, so if you keep Norton, just have the rest above except the anti virus ones . Some will say the W7 firewall is ok.
AVG Anti-Virus Free Edition 9.0 provides essential anti-virus and antispyware protection. The software also includes the Free AVG LinkScanner, discussed in Bright Hub's article Free AVG LinkScanner Review, to protect you from fraudulent sites. Among other advantages AVG Anti-Virus 9.0 (not Free) extends the AVG Free edition’s basic anti-spyware and antivirus protection with anti-rootkit functionality as well as Webshield to safeguards your downloads. The AVG Anti-Virus license is $34.99 for a one year subscription which includes free support. For twenty dollars more you can obtain AVG Internet Security 9.0 which extends AVG Anti-Virus 9.0 and includes identity protection, anti-Spam features as well as an enhanced firewall for example.