ddr2 667

Hi, My old LGE50(ED500) laptop used to run on 2GB(1+1) DDR2 rams of 667Mhz individually. I tried upgrading to 4gb(2+2) of both 800Mhz speed. But the combination doesn't work. i get horizontal lines on screen at starting of LG logo and freezes there. I tried with 2gb(800Mhz) in second slot...

Hi Everyone, My laptop is hp c6720s core 2duo t5670 processor, window 10 installed. It's working fine with 2gb ddr2 ram in one slot. when i put another 2gb ram in another slot (total 4b gb in two slots), then it's start crashing on window home screen. Anykind of help or suggestion will be...