While Blizzard has not given any official word on Diablo III’s minimum system requirements, the Diablo 3 Beta shared that info with site reader Felis when he tried to install the beta client on his older machine. You see the message he received below, and those minimum specs are quite similar to the StarCraft 2 system requirements .
In related technical news, if you are worried about your graphics card not being able to support the game, a list was grabbed from the Beta client highlighting supported cards and expected performance from the different models. Well worth checking out. Thanks darcinx.