Both the retail box and Symantec website state that only certain versions of Windows 7 are supported by Norton Antivirus 2012: Professional and Enterprise are not listed. I can understand why Enterprise is not supported, as that is for IT departments, but why is Professional not supported? Is it because Professional can "Connect to company networks easily and more securely with Domain Join" as Microsoft's website states? What if I run Professional as Home Premium, in other words, only use the features Home Premium provides? I am using Professional at home on a single non-networked PC, so I cannot understand why Norton Antivirus 2012 would not work just fine.
Hello.
I wouldnt worry about it. Windows 7 Professional is fully supported. I am currently running Norton Internet Security 2012 on Windows 7 Professional. Most likely it was just an error on Symantec's part. Norton Internet Security contains the core components of Norton Antivirus, so if I can run NIS 2012 on Windows 7 Professional you can run NAV on Windows 7 Pro as well. Hope that helps you out.
No problem. I am running NIS 2012 on my laptop which has Win7 Professional 64-bit. 
@ beroque-quest,
From Norton Support here:
System requirements for Norton AntiVirus 2012
System requirements
To successfully install Norton AntiVirus 2012, your computer must meet the following minimum system requirements
Operating Systems
Microsoft Windows 7 (32-bit and 64-bit) Starter/Home Basic/Home Premium/Professional/Ultimate