intel mac will not boot

Hello

since yesterday my mac unbootable After installing a pack of police character. To be precise, it starts a boot and gets stuck on the screen where you see a little ball that turns showing it is working, but no end (I left it running for over an hour see ...)

By cons, j'avaisi installed Boot Camp (there lgtps) and if I use the option key, he offered me the choice of system startup. The partition pc starts normally (this is how I can get connected to find a solution if I choose the mac partition, even before pbe!

My mac is intel imac mac osx 10.5.6
thank you for your presence

You're going to need to give us some more information:

Do you have a backup? Time Machine?

Your Mac year and model? What did you install that caused your Mac to not be able to boot?

Have you tried to boot your Mac using Safe Boot Mode? Hold down the SHIFT key as soon as you hear the chime. If you can get into Safe Mode, try removing whatever it is that you installed.

Otherwise you might be faced with having to reinstall OS X.

Regards.