Could i put a i7 & gtx570 in my gateway dx4840 11e?

Unfortuntley No, You will need to upgrade the power supply to at-least 500Watts+ The DX48040 Only has 300 Watts of power, and that is not enough for a new powerful and GPU. I reccomend these psw's http://www.newegg.com/Product/Product.as…

http://www.newegg.com/Product/Product.as…

A i7 will not go into your computer as a I7 is LGA1366 And your computer is LGA1156 for the cpu.

The best you can get for a cpu that matches your motherboard is a Intel Core i5.