install disk will not stay in

I'm trying to run the AHT from the install disk (OS version 10.5.2) and it will not stay in. The disk looks in perfect condition and other disks work fine.

Have an early 2008 Macbook Pro that is having issues that could be hardware related. Any other recommendations for running a hardware diagnostic would be appreciated. I have newer macbook pro to work with if I need target mode.