Hi, You should scan with Norton about every five minutes these days.....no, just kidding. It depends on what you are doing and how many others use the computer I suppose- if you or others are opening a lot of email and perhaps attachments, then scan them first- or if possible, have Norton scan incoming mail, it does work for some email programs but we have no way to tell....
A good time to run the malware detectors like AAW is just after installing some program, game, etc to see if it contains anything bad. Or, review well by searching online about the program before downloading it. Spyware is becoming a big issue and lots of sites have selected their downloads to screen out junk containing programs....some do not do this and you can download almost anything....
File sharing is another issue- if you do that, expect to be using all your "ammo" a lot.
You need to do updating every few days anyway, so a scan just after getting updates is recommended.
You can scan a download for viruses by right clicking and choosing "Scan with Norton A/V"....
The other suggestions in posts are also good advice...
