Factory Reset 10.6.8 HELP!

Is it a retail disk with a picture of a Snow Leopard on it, or is it gray? If the latter, you purchased a machine specific disk which will not work with other models.

Also, what model Mac are you trying to install SL on? Hold down the Option key and click on the Apple at the top left, then choose System Information. Note here what type of Mac it says you have. For instance, this is mine:

Model Identifier: MacPro5,1

What do you mean that the disc is not working? Is it damaged? Are you getting any error messages? Optical drive needs cleaning?

Your Mac is a Core Duo 2 and supports the Mac OS all way up to the current 10.8.x Mountain Lion. The retail disk should most certainly work.

Question. Is the drive you're trying to install to using a GUID partition map, or Apple Partition Map? Snow Leopard and later requires GUID. Though this isn't really the issue since your Mac isn't reading the disk in the first place.

When you say you've tried another disk which worked, was that another DVD, or a CD? It's an important distinction since DVD drives have two lasers. One for reading CDs, and the other for DVDs. So it's entirely possible to still read CD disks, but not DVDs if the laser for DVDs isn't working. Try any other disk you know is a DVD and see if it shows up on the desktop. Any DVD movie disk you have will do.

You can either replace the internal drive, or purchase pretty much any external USB DVD drive and use that for DVD disks.

Can't say as I've never tried it. Might be a problem though as the Mac will reboot once during the install of SL. It may not pick up the disk again to continue the install.

Good thing is, they're cheap. I bought a read/write one at Best Buy a couple of years ago, and it was only $40 or so. Looking again just now, they run anywhere from $30 to $360. I think a person would have to be a bit off their rocker to spend more than $80 on one.