G5 problem???

I have a G5 dual processor. I have Leopard installed Just about an hour ago I got a message that there were some software updates. When I checked them there was one for iTunes and one for Leopard. I went ahead and installed them and when the restart took place up came the gray apple with the little wheel and that's all the further it went. The fans began to blow full tilt and it went nuts so I shut it down by holding in the start button. I then restarted it and again it has gone to that same screen and no further. It just sits there and spins. Any suggestions?? It has now been doing it for about 15 minutes. Any other way to get around it???

Thanks

 

Maybe I wasn't clear. I have had Leopard installed for about 3 months. Just today I got a notice from the automatic software that there were two things to install. One was an update to iTunes and the other an update to Leopard. I went ahead and installed them both and waited for the restart that is automatic when the software updates are done. It tried to restart but only goes as far as the gray screen with the apple and little circular spinning wheel. It will do nothing more, just sit there and spin. For more than 20 minutes. Leopard has been working good up until this happened today.

 

Tried it but still nothing but the spinning wheel. If I could do it I would remove Leopard and go back to Tiger. But I have to get it up and running somehow. It was working fine until this last update!

Thanks

 

By the way, I also have MacBook Pro. Any way I could start the other computer up in T mode and put the hard drive on my laptop and then copy it to an external drive and then possibly reinstall the OS on it??