Cant boot it, won;t get past the grey screen and spinning wheel

First: If you can boot with DVD, load your install disk and "run repair" from "Disk Utility". If you do not have the disks you might find them on ebay. Another option is to run a disk called "TechTool Pro" It will fix some stuff that Apples Disk Utility doesn't.

Second: Another option is to try and start up in safe mode and see if you can get to desktop. To open in safe mode, Restart and as soon as you hear the startup tone hold the shift key down. Keep holding until you get to the login screen. Yes, you may have to enter your login info and password. If you get there from safe mode, be sure to backup anything you can before restarting.

That is what I would do if I got what you describe.

I would also zap the PRAM by holding down the option-commmand-P-R keys right after you hear the startup tone. Continue to hold these keys down until you hear the tone two times. The screen will most likely go black between tones. Then let go and see if all works.

Good luck