I just finished building my first computer but the motherboard light doesnt ligth up everything seems to be connected fine can i have any suggestions. Thanks. the mother board is a asrock h61m/u3s3. And the psu works fine.
Try to power the board by shortly connecting together the two pins corresponding to the power switch. If still the same, and you know for sure that the power supply and the connections are OK, then it might be a faulty motherboard.
The two wires corresponding to the chassis power switch are connected to a motherboard header (where you connect the reset switch, the HDD led a.s.o.)
Check the manual for the right position of the two pins corresponding to the power switch (see system panel connector).
Remove all wires from that connector and using a screwdriver shortly touch the two power pins (it's what the switch does when pressing it). The switch might not work, the wires might be interrupted.
Turn off the power supply and check if the 4-pin or the 8-pin power connector is connected. Connect also a case fan to the PSU's molex or to the motherboard header.
Switch ON the power supply, start again the board (by shorting the pins) and check if the CPU and the case fans spin.