I decided to collect a computer so i bought an asus P5ql motherboard,a 500 gb hard disk,a cpu and a dvd drive.(i have the PS and a cas)
after putting everything together i started the computer and it worked and i started to install window,but i noticed a sound coming from the cpu fan si i shut the computer down and replaced the fan by removing-i had to remove the motherboard then return it again-
now when i plug it the motherboard's light lights up meaning that the power is there but when i press the butten nothing happens..the fans dont work and no lights are on other than the one i talked about before.

what seems to be the problem?

thanx in advance

"A sound" makes it difficult. Was it mechanical, like the fan banging on it? Do you really mean the CPU itself? With brand new builds like this, I would take everything out of the case and start over ensuring you have NO extra standoffs under the board, and everything is connected properly - including all power connectors.

Did you use, TIM?

the sound of the fan is not the problem,i know why my fan makes sound because it is touching something while spinning,i wanted to change it anyway because i have a better asus fan

i didn't use TIM and i've never known i would need such a thing because i had 3 computers before and they had nothing like that

keep in mind that the computer worked great the first time before i removed the motherboard but now it is not working at all

i think it might be the (power sw) coming from the case that connects the motherboard to the on switch-the bpower-what do you think and what should i do if it is the problem?

i didn't use TIM and i've never known i would need such a thing because i had 3 computers before and they had nothing like that

That would not be likely, unless they were all home built by someone who did not do their homework. CPUs have come with little tubes of white silicon "grease" (not really grease, but that's what it was called) or thermal "pads" that melt, for, well, decades now. And when they don't the instruction still say to use some form of TIM.

keep in mind that the computer worked great the first time before i removed the motherboard but now it is not working at all

And that's possible - a CPU hardly works at all until the OS is up and running and the computer is being used. And if the mating surfaces are clean, tight, there is some transfer.

I would still look for extra stand offs, and verify all motherboard power connections have been made.

If you disconnect everything from the motherboard except one stick of RAM, the monitor connection, and PSU, and reboot by shorting the two power switch pins, you should see on the monitor the initial boot process, graphics splash screen then it will fail when it cannot find a boot drive. If you don't get that far, you have other problems.

oh you are talking about the cpu! i didn't install the cpu,the guy i bought the parts from-a friend-installed it for me saying that it might be hard for me to do it my self.

the first time i reached the part where i started installing windows from the cd

anyway thank you for your help,taking it to an expert seems the only way

anyway thank you for your help,taking it to an expert seems the only way

There's no shame in that.