The general requirements for running FEZ is listed above along with some other information on the hardware specs below. Because that FEZ is a 50v50 game, the requirements have been slightly exaggerated to allow better quality while playing. Although do take in mind that this game is quite the RAM hog so some specs may not be exaggerated at all.
The game is optimal with Windows XP, however may have conflicts with the 64bit XP. Works with the other versions of windows quite fine. May not work well with Brazil Win7. Info about Mac OS is a little unknown but FEZ is known to be playable with it. (Bootcamp)
Duo or quad-core is more than enough for this game. FEZ isn't really a CPU-intensive game as it's more a graphic intensive one.
General recommendation is at least 2 GB minimum for FEZ as it is a very bad RAM hog. Otherwise remember to shut down all other programs before playing FEZ
Just don't integrated cards and you'll be fine.(integrated cards do work okay but isn't really well suited for FEZ, a graphic intensive game) Note that limiting your FPS is very recommended since FEZ doesn't have FPS limiter (exception of JP) otherwise you'll be using your graphic's card to its max.
5 free GB in case of updates
Latest version must be installed in order to play FEZ. Install the Direct X 9.0c distributable. If you do not install it the game will not run after pressing start and you will see a dark screen.
Do NOT use Dial-Up I heavily stress this Basic DSL is fine for FEZ just make sure no one is using your bandwidth while you play or you'll have your ping suffer as a result. Did I mention not to use Dial UP? DO not use Dial-Up or else you will not enjoy this game properly.