Thread: PC wont boot

I have issue with one of my older PC's when turned on it wont boot only loud noise comes out of it, screen is black on the monitor,no beeps or anything else .I tried to locate the noise and i think it is comming from the CPU fan making a noise as a jet engine.I replaced the GPU(8800GTX) with a 6870ATI with no results,pulled out the RAM one by one (dual channel MOBO) and replace them with new ones(DDR2 Nunuya 800Mhz 4x2Gb) still nothing,replaced the motherboard battery with a fresh one ,disconected two of the three HDD,Replaced the CPU cooling unit with new one and still same problem .Last thing i have to do is to try and replace the PSU with a new one, but before i throw my money on something i am not sure it will work(i dont have a spare PSU) i need some feedback here ,anybody familliar with this kind of issue?
any feedback is welcome



p.s. forgive me for my bad english thanx in advance