If your MacPro has a Kernel panic, the report is saved in a battery-backed RAM area and copied into a log at next startup. These reports can be read out later using this article.
Are you trying to repair your disk drive?
What about just what version of OS, what model Mac (iOS does not run on Mac), graphic card and other pertinent items.
There is nothing in your post to suggest why without digging and troubleshooting.
Want to find why, or how about just do a clean install on a new drive
move all your home folder to 2nd drive (never good to have it on boot drive anyway)
When you get done installing, don't move anything to the new system until you know it works
General purpose Mac troubleshooting guide: Isolating issues in Mac OS X
Creating a temporary user to isolate user-specific problems: Isolating an issue by using another user account
Identifying resource hogs and other tips: Using Activity Monitor to read System Memory and determine how much RAM is being used
Starting the computer in "safe mode": Mac OS X: What is Safe Boot, Safe Mode?
To identify potential hardware problems: Apple Hardware Test
General Mac maintenance: Tips to keep your Mac in top form
1. Insert the Mac OS X Install disc that came with your computer (Edit: Do not use this disc if it is not the same general version as what you have currently on your computer, e.g. use a Tiger disc for a Tiger drive, not a Panther disc), then restart the computer while holding the C key.
2. When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu. (In Mac OS X 10.4 or later, you must select your language first.)
Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.
3. Click the First Aid tab.
4. Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
5. Select your Mac OS X volume.
6. Click Repair. Disk Utility checks and repairs the disk."
Then boot in Safe Mode, (holding Shift key down at bootup; takes longer to boot this way so be patient), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, reboot when it completes.
Mac OS X: Starting up in Safe Mode - http://docs.info.apple.com/article.html?artnum=107393
What is Safe Boot, Safe Mode? (Mac OS X) - http://support.apple.com/kb/HT1564
Safe Boot takes longer than normal startup - http://docs.info.apple.com/article.html?artnum=107394
Bad cables. Bad drivers. 3rd party apps. Bad sector on the disk drive. Bad directory on disk drive. Corrupt files and caches.