Win7 is much more secure than XP or Vista (but less than Linux/Unix/OSX)
Stick with MSE - don't install AVG in parallel, it adds little and will clog your machine up.
Run Malwarebytes once a week
Don't open unknown emails & don't visit warez sites
Opera is a great (and less used/targeted) browser with a good email client
Sudo for Windows is a great (and free) utility -
Sudo for Windows | Free System Administration software downloads at SourceForge.net - logon as an ordinary (limited) user and elevate privileges as needed.
Sandboxie -
Sandboxie - Sandbox software for application isolation and secure Web browsing - is good if you are feeling adventurous (mostly free but worth the registration).
Mac
A known-good system image to off-line storage is reassuring
An off-line/off-site backup of anything important is mandatory.