PC port of SFIV will not be out until quite a bit later this year (they haven't even announced a release date yet I think). Right now the only way to play it is on a PS3/XBox360.
P.S. - If you do get it on a PC, don't get two XBox controllers for it, they are supposed to be horrible for this type of game due to the inaccurate D Pad design. What you want are arcade sticks.








