dai

have you plugged the aux power plug into the m/b
what brand is the 400w it is a bit light on for the system
try a cmos reset
turn the computer off
remove the power lead from the back
take the side off
remove the cmos battery
move the cmos jumper from pins 1 and 2 to pin 2 and 3 and the back to pins 1 and 2
replace the battery
put the side on
replug in the power lead
boot the computer
when you do get it to post you will need to do a reopair install of the op.system because you changed the m/b