I can't turn my new self-built computer on after I have put all the component into it.I dont know why, the power supply doesn't even on and the motherboard led also is off. The processor I am using is Pentium 2-355mhz slot 1 and motherboard Specifications: It has a BX-TOO Chipset which supports Intel Pentium II 233 - 500 MHz and Intel Celeron 266 - 433 MHz CPU Processors Supported with both board frequencies at 66/100 MHz in its Slot 1. Memory: 256 MB PC 100 Kingston RAM. Case: ATX Case. Anyone know how to solve it ? thank you.

Have you rechecked the connections leading from case power on button to mobo power button pins as well as connections to case led indicators? Reseated the power supply to mobo plugs? ETC. Do a check list of ALL connections and switch and/or jumper settings per your manual. If All is as it should be , then suspect power supply.

Turn the power supply switch on the back off. Short together or put a jumper on the two pins that take the leads to the switch on the front of the case. Now turn the switch on back on. If the fan does not turn, you have a power supply failure or it is the way it is hooked to the motherboard. You know that switch on the front is like an auto horn? A momentary contact turns the power supply on and you cannot turn it off there. Windows 9xx turns the computer off automatically when you select shutdown or you have to use a power strip or the switch in back. So with the switch in back on the power supply on, you have to touch the two pins that supply the front switch to make the power supply work. (As I recall turning the switch in back on and off will make the fan jump even if the pins are open. So an absolutely dead fan when that switch in back is moved would be a power supply or power cord problem.