This is one of the most frequently asked question by the developers when they want to develop Windows Phone 8 apps.
Can Windows Phone 8 SDK be installed on Windows 7?
Installing Windows Phone 8 SDK on Windows 7 is not officially supported.
The Windows Phone 8 SDK requires Windows 8 64-bit (x64) for it to be installed. The Windows Phone 8 emulator has an additional requirement that the Hyper-V is enabled in the system along with the Windows 8 Pro.
Now, how do one install Windows Phone 8 SDK on Windows 7?
I came across an interesting post in Nokia Developer Forum “Windows Phone 8 SDK on a Virtual Machine with Working Emulator” which explains how do install it on a Virtual Machine.