14 DAY TRIAL // When the system requirements for StarCraft II: Wings of Liberty were first announced, it was clear that Blizzard was not aiming to include very old computers anymore. Running the game in medium details at a decent resolution requires a stronger machine from the part of the user. The official U.S. forums contain a post detailing exactly what kinds of processors and video cards can handle StarCraft II's eye candy.
Those who own microprocessors produced by AMD should be aware that the old Thunderbird Athlon models cannot run the game. Athlon XP models that have a rating higher than 2200+ are supported. AMD Sempron types need a high clock speed. Those who have first generation AMD Phenom processors should be aware of a fix detailed on the official World of Warcraft forum. There will be no issues with Athlon II and Phenom II models.
On the Intel side of things, Pentium III processors will not play StarCraft II. Furthermore, Pentium IV and Pentium D models have to run at 2.6 GHz to be able to cope with the game's requirements. Core 2 processors are recommended to have a 2.5 GHz speed, but anything around 1.8 GHz will be able to run the title at low settings. Intel Celeron is quite a wide family of processors that is based on the architecture of the ones presented above. Different origins will result in different frames-per-second. All Core i3/i5/i7 models will have no problems with StarCraft II.
The Nvidia GeForce 6600 and ATI Radeon 9800 video card are just a guide. A performance chart available on Tom's Hardware shows that some higher-numbered card will not work with StarCraft II. Blizzard lists the most common cards that will not be able to run StarCraft II. They are NVIDIA GeForce 6150, 6200, 7150, 8300, 8400, 9100, 9300 and ATI Radeon Xpress 200, 1150, 1250, X1050, 8500-9600, X300-600. Most Intel GMA graphics adapters are under the title's system requirements.
A broadband Internet connection is required to install the game and for the online features. The single player campaign can be played offline using the Play as Guest menu or a Play Offline option that comes out when the game cannot connect to Battle.net. Achievements cannot be earned without an Internet connection.
Update: Corrected the article after testing the information reader Mark has provided. Thanks, Mark!