Don't worry about ebay - The disks I got were fine, the non boot up problem maybe because someone bought the install disks that came with a specific machine rather than the retail copy of tiger that will install on any machine.

Also make sure you don't buy tiger upgrade disks, since you will need to have 10.3 for them to work.

If the ebay seller shows photos of the disks they should look like this

http://i9.ebayimg.com/03/i/000/b6/70/7483_2.JPG

Black with an X on them, if they are grey - then they are for a specific machine. Make sure the disks are full install disks - not the upgrade

There seems to be plenty of Tigers out there - just make sure they are the full version and you will be fine.

Good luck