Ok, so Im building a barebone kit for a family member, I have built many before, but this one has me. On the ECS NFORCE6M-A2, I go by manual specs and insert 2 sticks of OCZ Gold 10666, 1333Mhz into the board, as it comes in the kit with (2) 1GB sticks, into DIMM 3 and 4 as it says for Opt. performance, and it will cause Windows to crash as its loading. Take a stick out from DIMM 4 and it works. Insert 2 sticks into DIMM 1 and 2 as indicated for normal performance, same issue. Insert 1 stick into DIMM 1 and it operates fine. I was thinking Voltage but I didnt want to change anything in the BIOS without consulting a secondary opinion.
Lmeow is right, we need to know the exact RAM kit you have so we can look up its rated timings and voltage. You should manually set the RAM speed, timings, and voltage to their rated values in the BIOS. It would also be a good idea to perform an overnight Memtest86+ test to check for faulty RAM.