When I start a new program, I get program not responding messages and it just stops. I am running windows 7 on an IMAC

I am running an IMAC with an I-5 Intel processor. I have installed Windows 7 and not OS-X. Had to install drivers for mac hardware that works with Windows 7.

Computer seems to run fine. However, sometimes when I start a new program I get the message "{Progroam Name} is not responding" then I have the open to wait, continue or quit. When I select quit the message says "Windows is searching for a solution to the problem" Is there something missing on my PC that is creating this freezup?