Will my computer run these games on med/high settings?

It depends on what resolution you are running at. For 1920x1080 you can definitely do medium/high for all those games. You won't be able to pull off ultra on Crysis 2 or BF3. Ultra settings on Skyrim does seem to require a lot of CPU horsepower, your card may be able to pull it off, but your CPU may be a bit too slow. Skyrim likes having 2 really fast cores rather than 4 slower cores. If you are running at a lower resolution you will see even better performance with the 6850.

As far as GTA IV goes, it is a really badly ported game that doesn't run all that well even on really good hardware. I have an i5 760 at 2.8GHz with a 6870 and the game will still hit occasional lag spikes when played on high settings at 1080p. Maximum settings won't be possible with a 6850 as GTA IV wants at least 1.5GB of video RAM for max settings, making it one of the only games where it is worthwhile to have a 2GB card.

400W won´t be enough for a HD 6850.

500 Watt or greater power supply is recommended. Refer to http://ati.amd.com/certifiedPSU for a list of Certified products

Thanks for the quick replies!

Though i'm actually running a resolution of 1440 x 900 haha

but yeah and to jemm... i said 400w isn't enough I guess because that's the one I have right now!  

I'm getting a 600w psu so it won't be a problem. Yeah, I wasn't expecting Ultra settings with this card... do you think the CPU is bottlenecking the card though?

and btw..I'm not sure what your playable fps is..but mine is 35 and up, just because i've lagged in games so much that i got used to it!  

Do you think I'll be able to run the games atleast 35 fps? personally i can't tell much difference between 35 and 60 fps.

At your resolution you'll be able to get 35 FPS and up with a 6850 on most of those games on ultra. GTA IV and Skyrim may be CPU bottlenecked at that resolution, and with Crysis 2 you would have to turn a few settings down to get an acceptable framerate. For most titles, the 6850 is actually more than you really need, and your CPU is more likely to hold you back for the most part. If possible, try overclocking your CPU, that will definitely help performance at your resolution.

Yeah i've been searching for for cpu overclocking guides on my cpu.. but i fail to find any  

i'm kind of a noob when it comes to overclocking  
I'll see what the graphic card can do when it gets here and ill go on from there..i probably wont need to overclock the cpu but who knows

Well, anyways thanks alot for your help!  

6850 is pretty comparable to my card setup - two 5770's in Crossfire, and I can run all of those games on at least "high", with playable FPS. (Which in my opinion is 50+). I play at 1920 x 1080 too.