What exactly did you try to fix the loud CPU?
Check or change all of your cables and connections. Examine the mobo and CPU carefully as you power up to see if the fans are running and where the noise is coming from.
When you power up is the BIOS posting first or just the blinking cursor? What else if anything do you see on the screen?
Did you test the HD and RAM yet from the steps I gave you? Swap RAM sticks to check no debris is in slot.
Do you have a video card or other PCI card in slot? Try uninstalling and then reinstall it, checking connections carefully.