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Quite often this is a sign of a bad MOBO, and shorting a PSU only means it's not completely bad.
What I would 'try' first is a proper Clear CMOS, unplug the PSU for 5~10 minutes to allow a full discharging then use the jumper method using tweezers if needed (most of the time you do); see -> http://www.youtube.com/watch?v=rdHH9KrceR0
If that fails then 'try' booting with (1) stick of RAM in the 2nd DIMM slot from the CPU. Failure again, try the other stick in the same DIMM slot.
Q - can you post and get into the BIOS?