It's hard to guess what the biggest bottleneck might be, Dabz. Is it thrashing the hard drive much during gameplay? The CPU and the videocard are not awe-inspiring, but I played Far Cry very nicely on a similar setup when it first came out. The main noticeable difference is that I had a gig of ram. I also had a Radeon 9700 too, but I don't think that's *much* better than a FX5600.
I'd just be concerned about recommending you get a new videocard in case the bottleneck is the ram, or something else.
I'd just be concerned about recommending you get a new videocard in case the bottleneck is the ram, or something else.