Should I store my PROGRAM FILES on my OS partition?

Generally, everything that you install (Windows + applications + games) should be on C:. All user-related data (movies, pictures, downloads, whatever) should be on another partition. That means that all personal data is NOT on your C, only the program data which can be replaced.

If you separate user-files from system-files, it would be easier to backup your stuff, and the C: drive will become less fragmented with your personal stuff - so its good for performance also.

Please note that antivirus programs can drastically reduce system performance. Every I/O will be checked by the anti-virus application first, slowing down the entire computer. An antivirus program is also a 'last resort'; it means a virus was able to come into your system in the first place. Ideally, you do not want a virus from ever reaching your computer.

Virusscanners protect against some static known virusses, but not against the much more dangerous and wide-spread spyware, adware and root-kits. No anti-virus company can keep up with the volume of new spyware being released into the wild every day - they may block some older spyware; but i would say they only cover 10% or less than what is available on the internet.

So in reality, a person without virus-scanner but a properly configured system would be more safe and enjoys a PC without slowdowns, than someone who installs all known virusscanners on the planet, but has a dangerous lifestyle of downloading 'funny things' from the internet; and such.

I never used a virus scanner on my personal system. I also never had any virusses that penetrate my network configuration. Having a virus-protected router means you protect your internet connection for all computers connected, without slowing them down.

Great answer, thanks. So it seems to me that most everything is dependent upon the OS, registry, program files folder, etc...for Windows (and my) well being. So I should install things like: driver discs, video games, Adobe photoshop, iTunes, things that make the computer "run" and that I use (programs I guess) into the OS partition so that they can all live together and be happy? Then store pictures of my kids on E:? Sounds logical, but what about people talking about an OS partition only? And getting a 30GB SSD for an "OS boot drive"? Surely I can't store all those program files on there too...? I feel like I'm missing something. Should I just say the hell with it and make the whole 1TB the C: drive, forget partitioning, and go have some lunch?  

Ohhh, I like the sound of that. Any recommendations? Link for learning? That would be nice...

If you want to learn about all sorts of security issues, listen to security now on the twit.tv podcast network. If you only listen to one episode, I'd recommend 'the rational rejection of security advice'. If you have time at work where you can listen to stuff like I do, the 200+ episode history of this podcast makes the day go very fast.