Can't use AA on Far Cry 2?

Your 4850 can run Crysis on ultra high? at what res?

You have to be at 1024 or 1280 resolution then?

I found that with a 4870, turning on U.High shadows kills my FPS. I have to settle for U.High everything except shadows set to V.High with 2xAA for one 4870.

8xAA with two of my 4870s drags it down to unplayable...you won't hit 8x with one 4850. 4x even on one 4870 IMO is not very smooth. You are setting your sights too high there champ.

It also could be a driver thing if you don't fully uninstall your previous versions but.....8xAA with one 4850 is asking for too much

Edit: Oh yeah, also make sure that you aren't going through CCC for AA. It doesn't do crap yet it hits your FPS still. I set all of the AA setting to use application settings...it helps up your FPS.

Its gotta be a low resi coz OP wants AA.

I cant get anywhere close to ultra high at any kinda decent resolution

On my machine I use a 22 inch widescreen monitor, so I have the resolution set to 1680 x 1050. Even so Crysis is fine and I know for a fact my machine is more than capable..I'll deal with it, but I can find a way around it. I know turning the res down makes it run smoother and I can put the AA on then but It doesn't look as good y'know?
To be honest you don't need that powerful of a machine to run games nowadays, my brother has a p4 extreme oc'ed at 4 ghz and the same graphics card as me with only 1.5 gb ram and he's running Crysis as good as I am on the highest settings.

I think maybe running highest details on DX9?

I have XP Pro SP3 so yeah I'm using DX9

You don't. I was playing COD4 on my P4/AGP 6800GT system over the break just fine. You just can't expect 8XAA out of such a system though. So do you play at 1680 all of the time or bump down? When you play at anything less than your native res and play in full screen mode, you are just zooming in and making it look like crap. If you don't do full screen it will look fine.