RAM question about frequency

[Ash9412]

I have 2x ddrII 2gb stix 1066mhz since i cant find 2 more can i put 4x 2gb but at 800mhz?Is it so big difference?

 

[clutchc]

About 266 MHz... ;-)
Actually, I doubt you'll even notice the difference. You can use the mix, but all RAM will run at the lower speed.