Dell dimension motherboard. help.

I have a dimension e510 desktop that is not booting up. I got it a few months ago, cleaned it then left it sitting in storage. I finally go back to it to fix it up some more and it would not start. There was a short in the PS so I replaced that and added some RAM. Now when I go to boot the computer up it cycles through the DELL boot screen and never even goes to windows it also is not recognizing the USB ports.
It also seems to shut down the hard drives (there's a clicking sound everytime the cycle repeats). I've taken out the new RAM just in case that was the issue and without the RAM the computer won't start at all. I'm wondering if there's a way to tell if it's a MB issue or a HD issue and how do I fix it... Thanks in advance!