quartus 9.1 and nios 7.2

what exactly do want to know ?

installation of quartus 9.1 & nios ide 7.2 ?

or software design with nios ide 7.2 but fpga is done with quartus 9.1 ?

or designing your application on both version ?

a nios fpga design created with 7.2 can be opened with 9.1 (updated) and recompiled.

as i do not use the ide (now) i can't tell you if the ide itself is compatibel and can (well i guess it can) open a software project done with 7.2 but i guess there the ide has changed a bit so downgrading could be a problem, but i am not shure here ...