As Stooge said, a lot of people have this problem. If you do a search you will get all the info you need, it could be soooo many things. Adding to what he said.... if you are using ram that´s supposed to run at more than 1,8v you may need to get some 1,8v ram to POST it and get in the BIOS to change the ram voltage to what it´s supposed to be. Then change the ram stick and restart. Good luck.