2002.  Wow you got some mileage out of that board.  Most don't last that long.I was talking real world recommendation, not what's on the box, which I have not found to be accurate very often.  Running anything over C4 on 512MB is going to really be tricky.  You will probably have the most trouble rendering.  The dreaded memory allocation error is pretty common on C5, which is the main reason I went up to 6.  My current machine, I built specifically for using C6 Pro on.  Cost me just under $1K for the parts, but for the increase in productivity, it was worth it.  To be honest with a system that old, you really won't be getting the best out of either of them.  When I first got C4 years ago, I had a 512MB machine, which was a lot back then, but even 4 was kind of klunky on it.  You might want to consider upgrading to something a bit more contemporary.  AMD based machines can be built very inexpensively now, and work just as (if not more than) well than Intel systems.