Can't boot without Install DVD

My Macbook crashed after searching on a massive amount of files with PhotoShop. The next time I tried to start it, I got stuck at the gray screen that has a circle with a line through it. I booted up from a Mac OS X Install DVD (the original one for this machine, Snow Leopard 10.6 something). That worked. I ran "repair permissions, and that process ran for hours and the machine got very hot. I finally shut it off. Later, I reinstalled the OS X, ran "repair permissions" (the partitions all looked normal and the repair process completed in 7 minutes), and was able to get to my regular log in screen, the usual apps, etc. The iTunes icon in the bottom taskbar was grayed out (I might have deleted images related to that by accident earlier), but everything else looked normal. However, I still can't get the laptop to start up on it's own. The only way I can boot is from the Install DVD. I do have two partitions on this - one for Mac, and one for Windows. Can someone please suggest what else I can try, so that I don't have to keep booting from the DVD? Thanks!

I'm holding down the Option key and selecting the DVD. After I reinstalled Snow Leopard from the Install DVD, I was able to access my profile. However, once I logged out (to see if it would reboot without the DVD), I'm back out at the Disk Utility (using the DVD). It does show both partitions. I just ran "Repair Disk" and it said everything seems to be okay. Is my only choice now to quit Disk Utility and reinstall the OSX (again)? The Mac partition only has 5.5 gb free (that is a little larger than it showed before). I'm not convinced that will solve the problem, since it didn't the first time - but if it's the only way that I can access my files, it might be the best option for now. I do have a one-year old clone from Carbon Copy Clone, and all of my recent files were backed up right before this happened. It's my son's computer. When I was able to get to the log-in screen after reinstalling OS X, his screen saver was the most recent one that he was using (he had added that particular photo in February). So I don' tthink we've lost any files, but I'm confused about why the reinstall didn't seem to work.

So to answer your question (sorry), System Preferences is grayed out and I'm at the Disk Utility screen, after having booted up from the Install disk.

When I hold down Option, I get three choices:
- The Mac partition
- The Windows partition
- The Mac OS X install DVD

When I click on the Mac partition, the Apple logo shows up with the spinning wheel. I can hear the fan and can hear the DVD drive being read. After a couple of minutes, I get the circle with a line through it (the symbol for "Do Not"), and the wheel (not a colorful apple) continues to spin. That's what it is doing right now.

By the way, thanks very much for helping me work through this.

This may not help but try booting in single user mode and running fsck. In earlier versions of OS X this command sometimes fixed things that Disk Utility couldn't fix.

I couldn't get the singke-user mode to finish. It got as far as checking for <dict =ID> and froze. The last thing it said was "still waiting for root disk"

I can get to Terminal Mode via the Install Disk's Disk Utility, but the command prompt on that says:
-bash-3.2#

Boot from the OS X Install DVD, and go to Utilities > Disk Utility and run Repair Disk. Sounds like the hard drive may have turned up its heels with all that work.

Thank you! I recopied all of the kext files (following instructions at iclarified #1119) via terminal, then saw your message and repaired the disk woth the Install DVD. After the disk repair, the "repair disk. option on the hard drive's Disk Utility was no longer greyed out; encouraging to see! I repaired the permissions again, followed your advice to reinstall Snow Leopard again, and everything looks good. Thanks to everyone who made suggestions to try. Now to make a new backup and try to get caught up on everything else ...

And with only 5 GB free space - don't really care what size the drive happens to be - that drive needs to have some space freed up - 5 GB is not even enough for the sleep image and virtual memory. And there is no doubt in my mind, it's running like molasses when trying to do much of anything.

Thanks. I've passed that on to my son, and we're getting a second external hard drive for stoage/backups.