New
#51
From what it tells you in the manual using 2 RAM sticks you should use the Blue, using 1 RAM Stick you use the first Blue and using 4 of course then the grey to. This is as far as i can see from picture and in the manual, but if look at the motherboard those numbers should be there A1, A2, B1, B2.
I understand it was just a suggestion on the Intel i7. What Brand and Model 750W PSU ? Hopefully that 2 year old WD was not the issue.
Since you ordered a new board i still wondered if you wanted to still try fixing this issue if you intend on using it still for a second PC.