Using two Operating System with all the requirements, yet slow, why?

I have installed two OS on my system i.e. Windows XP and 7. Here are the system specifications-
1. AMD phenom quad core processor.
2. 4 gb ram
3. 500 GB hard disk (sata)
The speed of games and video resembles tortoise and my XP became snail. What is/are the resolution(s) ?
