Snow Leopard won't install

Boot with your Leopard disc, launch Disk Utility, and repair the boot volume. If it reports the boot volume's OK, download and install the 10.5.8 COMBO update, repair permissions, and restart. Now, retry the SL installation.

You have a Leopard disc? If so, pop it in, restart, holding down the C key. Select your language, and when the menu bar pops up, select Disk Utility from the Utilities menu, select your boot volume, and click Repair disk. Details in http://support.apple.com/kb/ht1452

First, download the10.5.8 Combo Update here.

http://support.apple.com/kb/DL1324

Disk Utility is in Applications>Utilities. First verify the drive. Select the volume you normally boot from, which unless you renamed it, will probably be named Macintosh HD. If the message you get says everything is OK, then and only then, hit the Repair Permissions button for the same Volume. If errors are reported, then you will have to boot from the Install Disc (or a clone if you have one) and Repair Disk from there. See "Try Disk Utility" for instructions.

http://support.apple.com/kb/TS1417

Here's what I do for a major update. Maybe not all completely necessary, but I like the extra margin of safety. _The idea is to have a good, error free 10.5.8 in place before you install Snow Leopard._

1. Have a backup so if something does go wrong, you won't be left in big trouble.
2. Verify and if necessary repair the drive from Disk Utility. (To repair, you must be booted from the Install Disc or an external clone.)
3. Disconnect all peripherals except the keyboard and mouse.
4. Download the Combo Update. It's generally more reliable to update from the standalone than from Software Update, and the Combo, as it includes all updates from 10.6 onwards, may correct any files that have been corrupted or somehow gone AWOL (missing.)
5. Boot in Safe Boot. Hold the Shift key down at start up. Give it time, it will take longer. (The Safe Boot will also actually check and repair the drive if necessary--and if possible.)
6. Repair Permissions from Disk Utility while booted in Safe Boot.
7. Install the update from Safe Boot. Keep all Applications closed.
8. Restart when prompted and give the system up to five minutes to finish the final touches of the update with all Applications closed.
9. Verify the Drive and Repair Permissions again.
10. And then I like to restart a second time.

Oops wrong Combo update. Here's the 10.5.8

http://support.apple.com/downloads/MacOS_X_10_5_8_ComboUpdate

No, a backup really should be on an external drive. The whole point of a backup is if your internal drive dies or is failing, you can boot from the external (only if it is a clone) or restore from there with Time Machine, since it will be unaffected. In order to work properly an external drive used for a Time Machine backup should be much larger than the internal, maybe as much as 3X the size.

http://web.me.com/pondini/Time_Machine/Clones.html

What do you mean when you say, "should I try to download snow leopard again?"

You should be trying to install it from the Snow Leopard retail DVD, following Apple's instructions.

Also, I'm not sure how the advice to install the 10.5.8 combo update is supposed to help. The existing OS currently installed on the Mac is only used to launch the "Install Mac OS X" application, which performs tests on the Mac & target volume for the installation, & then writes pre-install files to it, at which point it (should) restart from the DVD to do the actual installation. Presumably, your installation has gotten this far but for some reason the DVD is being ejected when the Mac should be restarting from it.

I suggest checking the DVD for scratches or other blemishes. If it looks OK, try to start up from it by inserting it & holding down the C key on restart. If it still ejects, there may be something wrong with the disc that you can't see, or some problem with the optical drive.

One other idea. If you have set a firmware password, you may need to disable it for the installation to proceed.

Here's what should work:

1 locate the grey system disc which shipped with your Mac.

2 insert the system disc into your optical drive.

3 restart the Mac. Hold the 'C' key down as it restarts. The Mac should boot from the system disk, not from the internal hard drive.

4 select Disk Utility or Utility from the Install menu.

5 repair permissions.

6 fix disk.

7 reboot, this time not holding the 'C' key. The Mac should boot using the internal hard drive.

8 eject the system disc from your optical drive.

9 put the new Snow Leopard disc into the optical drive.

10 if you have not already downloaded the 10.5.8 combo update, do that now.

11 if you have not already made a backup of your entire internal hard drive, do that now. This backup must be on a separate hard drive from your internal hard drive, and must be bootable. I'd use a cheap USB external drive (1 TB USB drives are available for under $80) and either Carbon Copy CLoner or SuperDuper! to make the backup. CCC is donationware and SD! is shareware. There are other disk clone utilities; Drive Genius, for example, includes a disk cloner in its toolkit. I've never used that cloner because I use CCC, but if you have DG and you don't have CCC you don't have to download CCC if you don't want to. Note that CCC, SD!, DG, and other Mac disk cloners will clone the Mac partition, only. They will not clone the Boot Camp partition. If you want to clone the Boot Camp partition, and you should, you should get hold of a utility such as WinClone, a Mac app which clones Windows partitions, or any of the multitude of Windows disk clone utilities, such as Acronis True Image. Note that if you don't back up your system you may, and probably will, lose data sooner rather than later. There are two kinds of hard disks: the ones which have failed, and the ones which haven't failed yet. They will all fail. All of them.

12 launch and run the 10.5.8 combo updater.

13 reboot, holding the 'C' key. The Mac should start up on the Snow Leopard disc.

14 select Utility from the Install menu.

15 repair permissions.

16 fix disk.

17 select Install from the Install menu.

18 Install Snow Leopard.

19 reboot. The Mac should come up on the internal hard drive, running Snow Leopard.

20 download and install the 10.6.5 update and any other relevant updates.

21 keep the backup in a safe place until you are certain that all is well. If there is a problem, boot up from the backup.

It's not strictly necessary to do all of the above, but as you were having a problem, this will ensure that you can do things safely.

Frankendooglebert wrote:
This is what I've done:
-restarted the computer & held 'C' (nothing happened)

The C key will have no effect unless there is a DVD in the optical drive with a copy of the OS on it that can start up your Mac.

This is true regardless of what OS version is installed on the Mac's internal drive, or even if it is blank. So if you cannot start up your Mac from the Snow Leopard install DVD using the C key with that DVD in the optical drive, you can rule out whatever is or is not installed on the internal drive as the cause of your problem.

Try starting up directly from the DVD, using the C key with the DVD already in the optical drive.

Let us know what happens.