(I am not exactly sure if this should go in O'Club or Hardware and Software, seeing it is an issue that doesn't involve AH)
I can't help but to worry about a new problem my PC has gotten since I had to replace the PSU and Motherboard. (the PSU failure was an odd one as it was providing the right voltages and current, but would not let any PC boot up. Out of precaution I also changed my board out as well when I got my new Power Supply back in February of this year.)
The weird issue I am having now is once every couple of months my PC will fail to boot, It will not give a BIOS beep, and will display "..." in the upper left of the screen. followed by it shutting itself down. trying to restart it yields it giving its normal beep and merrily going into windows and will continue booting normally until it does this again in a couple months.
The biggest issue is I just can't seem to find anything wrong with the system.

Tried Prime95, Memtest, Intel's 'Burn test' , checked SMART on HDD several times and everything passes without a hitch.
So I have to ask as I think I have exhausted everything I can think of that can be wrong.

Any ideas of what could be going wrong?
(If more information is needed, Ill be glad to give it, I just don't know if there is a post size limit.)