One thing I like to point out is 64 bit windows,manufacturer(s) state maximum ram for your notebook.
Here they even released a later model than mine,but still state the maximum ram for my model range is 4GB.
This is shocking because after all the years I have own the this notebook, about 6 years old,it works fine with 8GB DDR2
So the short story is,if you have a 64 bit windows, you may want to check what is the "real" maximum ram for your computer.
I only checked because I found it strange to have a 64 bit OS and the maximum ram quoted by the manufacture to be 4GB.
Ensure bios & all drivers are up to date,check manufacture website.
ALL MODIFICATION AT YOUR OWN RISK