Dota 2

According to one of the DotA 2 website admins and possibly Valve employees or staff member, DotA 2 system requirements have finally been officially confirmed.
DotA 2 Minimum System Requirements:  

• OS: Windows® 7 / Vista / Vista64 / XP
• Processor: Pentium 4 3.0GHz
• Memory: 1 GB for XP / 2GB for Vista
• Graphics: DirectX 9 compatible video card with 128 MB, Shader model 2.0. ATI X800, NVidia 6600 or better
• Hard Drive: At least 2.5 GB of free space
• Sound: DirectX 9.0c compatible sound card

DotA 2 Recommended System Requirements:

• OS: Windows® 7 / Vista / Vista64 / XP
• Processor: Intel core 2 duo 2.4GHz
• Memory: 1 GB for XP / 2GB for Vista
• Graphics: DirectX 9 compatible video card with Shader model 3.0. NVidia 7600, ATI X1600 or better
• Hard Drive: At least 2.5 GB of free space
• Sound: DirectX 9.0c compatible sound card

Although it is known that Valve’s DotA 2 will be powered by Valve’s Source engine, various games featured different versions of Source engine and according to the earlier mentioned DotA 2 staff member, in case you can run Alien Swarm, you will also be able to run DotA 2 without a single problem.