We keep an updated set of full system requirements for Diablo III here:
http://us.battle.net/support/en/article/diablo-iii-system-requirementsThe minimum requirements to run the game can be summed up as follows:
PC: Fully-updated Windows® XP/Vista/7 with DirectX 9.0c, an Intel Pentium® D 2.8 GHz or AMD Athlon™ 64 X2 4400+ (or better), an NVIDIA® GeForce® 7800 GT or ATI Radeon™ X1950 Pro (or better), 1 GB RAM (with Windows XP)or 1.5 GB RAM (with Vista or Windows 7), 12 GB available Hard Drive space, DVD-ROM drive (for retail disc versions only), a Broadband Internet connection, and video settings reaching a minimum resolution of 1024x768.
Mac: Mac® OS X 10.6.8, 10.7.x or newer, an Intel® Core 2 Duo CPU (or better), an NVIDIA® GeForce® 8600M GT or ATI Radeon™ HD 2600 (or better), 2 GB RAM, 12 GB available Hard Drive space, DVD-ROM drive (for retail disc versions only), a Broadband Internet connection, and video settings reaching a minimum resolution of 1024x768.
Beyond the minimum requirements, we recommend the following for adequate performance:
PC: Fully-updated Windows® Vista/7, an Intel® Core 2 Duo 2.4 GHz or AMD Athlon™ 64 X2 5600+ 2.8 GHz or better, at least 2 GB RAM, and an NVIDIA® GeForce® 260 or ATI Radeon™ HD 4870 or better.
Mac: Mac® OS X 10.7.x or newer, an Intel® Core 2 Duo CPU or better, 2 GB RAM, and an
NVIDIA® GeForce® GT 330M or ATI Radeon™ HD 4670 or better.
We have a list of unsupported video cards for you here:
http://us.battle.net/support/en/article/diablo-iii-unsupported-video-card-listIf you have further questions about how your rig might mix with Diablo III, please ask them in this thread, rather than create a new thread on the subject.
Thank you!