How do I make my Windows 7 Hyper-V virtual machine full screen ?

Hi,

I'm running windows 8.1 as a host machine. I've installed Hyper-V feature and then I installed a windows 7 in a virtual machine.

But the pain point is it does not get full screen because it just hasn't the screen resolution I'm looking for. So changing the resolution is not an option since it says that my total available graphics memory is 8 mb. How can I increase this memory ?

My Hyper-V vistual machin configuration for windows 7 is :

RAM: Dynamic 1024 , CPU: 4 virtual