Hello Richard,
The Mac OS X 10.4 Tiger disk you have, it's the full retail version and not the upgrade?
What you might be best to do is do a clean install by first formating the drive.
Make sure you back up any files you wish to keep from your old OS.
Do the following;
1. Insert the Mac OS X Install 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 Erase 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. Highlight the drive, select Partition Tab, then Format type... MacOS Extended Journalled, select the Security Options button, choose Zero Out Data, Erase... after completion hopefully you'll be able to install.
Let us know if this works for you.
Best of luck.