System restarts 3 computers down

Hello,

this is SHIVA

i have a i3 processor.... and intel board....
the system shuts automatically, and some time restarts... but some times it doesnt restarts but the front light will be lit up..... the processor fan will be running but the beep sound when a computer starts, it doesnt come.... even after a day i tried to boot the computer it doesnt boot up.....
WHEN I change the ram slot it boots up...... then if i shut down it wouldnt boot up.....
then again i have to change the ram slot......
THINKING ON IT I LOST HALF OF MY HAIR......
sometimes i unplug the rom it would work......

i seriously dont know wat to be done.........

my computer worked for 5 months fine.....

the biggest head ache is i had 2 other computers which had the same problem.......

my electrical out put is fine.... its got the earthing connection --- checked with the electrician.......

thought it would be the monitor... changed it ---- still the same........

i still dont know what should i do........... please please please help me with this issue....