Mac Pro Wont Boot

My friend is stuck here.

If he could get into OS X he would have posted this.

He just ran the his software update and I believe it was just the latest Intel update for his Mac Pro.

So now, at restart, the machine gets stuck at the boot screen and just sits there with the spinning wheel. He's going to try booting in safe mode, but I had a similar problem with my MBP and safe mode didnt seem to do the trick. I ended up reformatting, which obviously he is trying to avoid.

Any help is much appreciated.

Thanks


..pCe..

Has he tried disk utility??

Put in the install disk and restart
Hold C while booting
Choose disk utility from installer menu
Click firt aid
click the triangle at the left side of the Hard drive
Select Mac os X
click repair