rescue deleted files from trash on a OC 10.5.8 system

Your post is a bit unclear. If you moved items to the trash, you should be able to drag them back out of the trash on the same computer. If you have deleted the trash, you will need to restore the photos from a back up. I'm not sure how the second computer figures into this.

Installing an app on the older Mac could possibly overwrite some of the files that you wish to retrieve. If you haven't written any new files to the drive since emptying the trash, you've only deleted them from the directory. They're still on the hard drive for possible recovery, but you'll need to do it from a 2nd computer. I'd remove the hard drive from the Quicksilver and connect it to the newer Mac using an IDE/SATA-to-USB adapter. It's not a platform-specific piece of hardware, so you can buy one from a PC retailer. As for recommendations regarding an effective data retrieval app, I'll leave that to those who have firsthand experience with a recent one.

So are you saying the older computer doesn't work anymore?