Windows phone 7 isn't windows, it's windows CE, BIG difference. it doesn't run software that you run on your home PC.
A lot of people have used variants of it since the 90's and it's always been a total dissapointment, not because of the available 3rd party software (there's plenty) but because it's basically always been a buggy POS that needs to be reinstalled more often than the PC versions of windows.
I'm pretty sure they could with some work run even windows 7 on arm, but, it still wouldn't be useful, since EVERYTHING for it is compiled for intel.

The marriage between intel+microsoft isn't going to end any time soon.