And there's no beeping sound, i ruled out the: power supply, CD-ROM, RAM. I thinking the hard drive might be the cause. I try to turn it on and it only reads the CD-ROM, but the CPU Fan is not spinning.
Try connecting another fan to the CPU_FAN header. It may be that something is damaged on the motherboard and preventing the fan from powering up. It sounds like you've taken your CPU out at some stage - did you knock any part of the PC at all?
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.
Make sure you plug the CPU power cable in. The system will not boot without it.
I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.
You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.
If no beeps: Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.
At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.
The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.
A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.
This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.
If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.
Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.
Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST. At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.
Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
Thanks everyone help and advice, me and my bro straighten the pins. After we left it alone for a night, And in the morning the computer turn on, and is still functional. Will the CPU stop function later on? compact SR159NX 2.5 GHZ (INTEL) 1 GB RAM. 40 GB Hard Drive. Any suggestions about the CPU? and If we can upgrade the RAM from 1 GB to 2.5? Only two slots. Planning on buying a 2 GB RAM. and Another hard drive too
All pc's have beep codes and typically 1 short beep means 'everything is ok' (on some systems its two beeps) so a 'no beep' situation means no speaker is installed or worse (the other things I mentioned).
Hmmmm, i have not git that a thought, one this computer that i mention; has speakers that are powered by USB. And i have run sfc /scanall in command prompt. and said there is some things that are not there. Originally it has come with home edition, put has XP Professional. On anther computer theres a beep, but i dont remember how long its it. (ill update on the other computer tomorrow)