As announced on the Battlefield Blog, the Battlefield Website announces open beta testing of Battlefield 3 will commence on September 29th, allowing early access to DICE's military shooter sequel for all three of its target platforms. There is a brief FAQ confirming that EA's Origin service will be required to acquire and play the Windows beta, and explaining how and when to qualify for early access, which commences on October 25th. They also offer system requirements, confirming reports that the game will not support Windows XP:

MINIMUM SYSTEM REQUIREMENTS
OS: WINDOWS VISTA (SERVICE PACK 2) 32-BIT
PROCESSOR: 2 GHZ DUAL CORE (CORE 2 DUO 2.4 GHZ OR ALTHON 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