HT1338: OS X: Updating OS X and Mac App Store appsLearn about OS X: Updating OS X and Mac App Store apps
Currently Being ModeratedMay 9, 2012 2:23 PM (in response to rica27)
Do you have a backup of your hard drive prior to the Leopard install attempt? You always should. If you do, boot from the backup and clone it back to your internal HD.
If you don't have a backup, boot from your Tiger installer disc and run Disk Utility Repair HD. You've probably corrupted some of the files, but possibly Disk Utility can repair.
Installing Mac OS X 10.5 Leopard
Mac OS X 10.5 Leopard Installation and Setup Guide
After you install the base 10.5, download & install the 10.5.8 combo update at http://support.apple.com/downloads/Mac_OS_X_10_5_8_Combo_Update
Does your Leopard DVD should look like this?