Windows firewall is pretty good on win7 - use that
Install MSE for antivirus - extremely good and very light on resources
install spyware guard - real time
download and use MBAM and SuperAntiSpyware - use regularly
Once a week, do E-SET online scanner.
The best part is all of them mostly are free for personal use. If you want, you may pay $25 to get MBAM pro for real time protection against malware....this would be a lifetime license for personal use....
I do not have a third party internet security suite on my win 7 64 bit systems.