Hello, I recently bought the parts for a pc online and I just put it all together. Everything seems to be working fine except my cd drive. When I turn on the pc it instantly ejects. If I push the button, it goes back in, but right away comes back out again.

this is a big issue, because I cant install the OS or anything without a working disk drive

thanks in advance.

also, there is a green light lit up on my mobo, dont know what that means

I would replace the IDE cable to the CD drive and while I was at it I would check to make sure I had it installed correctly. I would also check the jumper and make sure it was set to master or slave whichever applied. The green light means it is receiving power from the psu.

This is often caused when the front surround hasn't been fitted correctly (the draw switch doesn't see it closing correctly); give it a quick visual or a (very) GENTLE push, if that don't work RMA it.