With that system I can run CFS2 with alot of trees and even make some real nice forest and still come out way ahead. If I used a 32 bit OS such as Vista home Premium or XP would I get the same frame rates or do I need to run a 64bit OS?
The problem is that XP will limit the system and only allow you to use 3GB of RAM (4GB MAX. if you tweak it)
4+ GB of RAM works fine in Vista/Win7 32 & 64Bit - the only limit is the max. amount of RAM your motherboard will support.
I cannot give you a definitive answer in regard to framerate differences in 32bit vs. 64bit as I have not tested this.
However if you consider that a 32bit o/s is like having your data driving down a 32 lane highway ... and a 64 bit o/s has 64 lanes; then you'd have twice the data volume. Theoretically; I would speculate the 64bit o/s should provide better framerates over the 32bit o/s.
I have been using Win7 for about 8 months. Last Nov. I picked up an old eMachine PC (produced in 2006).