All digital devices have a system software which allows you to install the operating system on it. Now,in the case of the lumia,the system software will only allow you to install windows mobile and not android. You can not change that,that's how the device was programmed
Until nokia officially starts to support android,it may remain impossible to load android onto a lumia device,and for your own info,nokia and Microsoft are in a deal in which nokia agreed to produce windows phones exclusively for 5 years.