We tried 9.1 on a Win7 system and also saw odd things (I don't remember the details). Moving to 9.2 worked better, but that system has had problems with PADS ever since. Another system in the building running Win7 and PADS 9.3 works fine. $$$
I am running 9.3.1 and also really don't see any major issues with Win7 64 bit with overall running of tool.
But I will say I still have the Welcome Splash Screen problem, it is a variable problem, sometimes the screen does not come up at all (then I just use open),
sometimes it comes up like you say only half of it is visible (but you can see enough of list of designs to pick one) the other half is blocke off, and it actually sometimes comes up perfectly correct.
But I think this problem may not be related to WIN 7 I am pretty sure I saw it happen to me in XP also.
Maybe soem one form Mentor coudl step in about wlecom screen not viewign properly, I did a search on support net and found nothing on that.
PADS V9.2 is the first version supported on Windows 7 (both 32-bit and 64-bit versions).