First off, here's the rquirements for BF3:
http://www.gameinformer.com/b/news/archive/2011/09/21/battlefield-3-39-s-official-pc-system-requirements.aspx
Minimum System Requirements
OS: WINDOWS VISTA (SERVICE PACK 2) 32-BIT
PROCESSOR: 2 GHZ DUAL CORE (CORE 2 DUO 2.4 GHZ OR ATHLON X2 2.7 GHZ)
MEMORY: 2 GB
HARD DRIVE: 20 GB
GRAPHICS CARD (AMD): DIRECTX 10.1 COMPATIBLE WITH 512 MB RAM (ATI RADEON 3000, 4000, 5000 OR 6000 SERIES, WITH ATI RADEON 3870 OR HIGHER PERFORMANCE)
GRAPHICS CARD (NVIDIA): DIRECTX 10.0 COMPATIBLE WITH 512 MB RAM (NVIDIA GEFORCE 8, 9, 200, 300, 400 OR 500 SERIES WITH NVIDIA GEFORCE 8800 GT OR HIGHER PERFORMANCE)
SOUND CARD: DIRECTX COMPATIBLE
KEYBOARD AND MOUSE
DVD ROM DRIVE
Recommended System Requirements
OS: WINDOWS 7 64-BIT
PROCESSOR: QUAD-CORE CPU
MEMORY: 4 GB
HARD DRIVE: 20 GB
GRAPHICS CARD: DIRECTX 11 COMPATIBLE WITH 1024 MB RAM (NVIDIA GEFORCE GTX 560 OR ATI RADEON 6950)
SOUND CARD: DIRECTX COMPATIBLE
KEYBOARD AND MOUSE
DVD ROM DRIVE
How much are you looking to spend on this build? I'm guessing to run it on Ultra, you could probably build a fairly cheap rig with a Phenom II X4, and 4 gigs of ram. The GPU I'm not going to recommend, as I have trouble picking those out myself. More than likely, the most expensive part in the entire build would be the GPU. The rest you could probably do for about $300, but you should be prepared to drop a good chunk of change on a decent GPU and another $100+ on a decent power supply.
Another thing to take into consideration is the monitor you'll be using. A cheap monitor will just waste the graphics power, as well as using a lower end LCD or LED TV as a monitor.
Hard drives are also WAY expensive right now due to the flooding in Thailand. But if all you are going to use it for is a few games and basic browsing, you shouldn't need a large hard drive.
When I built my rig (My first "gaming" rig) I used the forums here and everywhere else to help me decide on parts. The folks here are plenty knowledgeable. If one person doesn't know, someone else will.
Best advice I can give is to ask questions. Lots of them.
Get several opinions on each question you ask.
Research everything.
Read reviews on multiple sites on any part BEFORE you purchase it to avoid a hassle later.
Try to avoid used parts from untrusted sources. (Ebay) The marketplace here is a great place to get good deals on used hardware, as people here aren't going to try and rip you off or sell you a bunk part.
Wow... Didn't expect so many replies by the time I finished writing. lmao
Edited by NeighborhoodGeek - 1/29/12 at 2:10am