Computer turns on, monitor goes to sleep. Help.

[sindraim]

Hello everyone, I made this account to ask for help.
Let's jump straight to the problem >
About a month ago when I was disassembling my computer, I accidentally dropped one of the screws from the side case into the powersupply, it's been standing there until today when I took out the PSU and shaked it out.
I then proceeded to put the PSU back in place and assemble everything as it was before.
Put the CPU in, the graphics card in, the RAMs in and then just plug in the cables.
Everything's fine until this point... when I turn the computer on, I get the noise of my CPU cooler, my GPU cooler, HDD and strangely enough my disc reader but no image or sound.
No windows welcome tune, no windows loading, no BIOS screen, nothing.
Just my monitor going to sleep and the noise.
The problem isn't with the monitor as I have it hooked up to another machine right now, along with the RAMs and the GPU.
The CPU has also been standing on top of my shelf for the month, could something have happened to it?
Or is the problem with something else?

 

[velosteraptor]

Well... first step is obviously the PSU.
Try another if youve got it. If not, maybe test all the cables with a a volt readerto make sure its putting out correct wattage. Or maybe even borrow one from a friend.