Game Turns to Black - When playing after 1 hour

I have a game turns to black all units when playing after 1 hr
As Austria Hungary in World War 1

I have laptop

4 GB memory, Windows 8 , Intel Core 15 4200 U 1.6 GHZ
500 Hard Drive

It says not enough memory but by previous computer

3 GB memory, Windows 7 , Intel Pentium 3
180 Hard Drive it can play after 2 to 8 hrs