On upgrading the RAM windows just dies

My Laptop supports max frequency of 8500 Mhz but I later I realized that I have installed a 10600S (2GB DDR3) in it and its working but its not sufficient for Windows 10. Its an old laptop and I think of using it as a server.

So I took a 4 GB DDR3 with 12800S (1600 Mhz) from my other laptop and installed in it, it POSTed fine but Windows is crashing. So I want to buy a RAM (1333 Mhz) but I don't know if it will work or not. The Samsung 1333 Mhz RAM stick is cheaper and 1066 Mhz Stick is costly, I know they run at lower frequency but will they run?