[ElDiabloConCaca]

That "gray screen with the turning wheel" you describe is the portion of the startup process where your startup disk integrity is checked and should not be interrupted. If you really have interrupted this process many times, you may have caused significant damage to the system install.

Reboot, and let it sit at the grey screen until it completes. It may take some time, perhaps 20 minutes or more, maybe even an hour or more, depending on how damaged the hard drive is.

For future reference, "pulling the plug" or doing a hard-reset should be avoided at all costs. UNIX/Mac OS X is VERY picky about shutdown processes, and doing a hard shutdown bypasses these checks and can damage the system install.

I would follow Pengu's suggestion, except you should be doing a "Repair Disk" while booted from the CD, not a "Repair Permissions." Repairing the permissions can be done safely while booted from the hard drive and is actually recommended that it be done that way. Repairing permissions, however, does not repair damage to the system, which I am almost positive you have since you've interrupted the repair process many times.

After everything is up and running again (after the repair has completed, either by letting the grey screen run to completion or booting from the CD and repairing the disk), then repair permissions to make sure that everything's in good, working order.

For an analogy, think of your OS X box like a car -- you wouldn't sit in the car with the key in the ignition, turning it on, then immediately off, then on again, then off again, then on again -- you're bound to screw the engine up if you did that. Same applies to the computer. If there's something wrong, turning it off and on and off and on and off and on over and over is bound to damage the system. If you suspect something is wrong, repair the drive by booting from the CD and then proceed troubleshooting from there. OS X, much like your car, will not magically heal itself -- if there's a problem, then more than likely one of us here can help you get it straightened out if you come here early enough in the problematic stages. If you let the problem go and keep shutting down and restarting a bunch, you may end up with an unrepairable system, forcing you to reinstall everything.