Restore MacBook Pro 2008 using Snow Leopard gives warning

Before Selling or Giving Away Your Pre-Lion Mac

1. Deauthorize your computer from iTunes, if applicable.
2. Back up your data using Time Machine or other backup methods for OS X Mavericks or Mountain Lion.
3. If you use Find My Mac or other iCloud features on this Mac, complete these steps:
   1. Back up your iCloud content.
      1. Choose Apple Menu () > System Preferences, then click iCloud.
      2. Deselect the Find My Mac checkbox.
   2. Sign out of iCloud. When you sign out of iCloud, you're asked whether you want to remove iCloud data from your Mac. Removing iCloud data in this way makes sure that the data isn't also removed from any of your other devices that are using the same iCloud account.
4. If you're using OS X Mountain Lion v10.8 or later, sign out of iMessage:
   1. In the Messages app, choose Preferences > Accounts.
   2. Select your iMessage account, then click Sign Out.
5. Follow these steps for installing the original version of OS that came with the computer.

1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

with your computer. Insert the disc into the optical drive and restart the computer.

After the chime press and hold down the "C" key. Release the key when you see

a small spinning gear appear below the dark gray Apple logo.

2. After the installer loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the Utilities menu.

After Disk Utility loads select the hard drive entry from the left side list (mfgr.'s ID and

drive size.) Click on the Partition tab in the DU main window. Set the number of

partitions to one (1) from the Partitions drop down menu, click on Options button

and select GUID, click on OK, then set the format type to MacOS Extended

(Journaled), then click on the Apply button.

3. When the formatting has completed quit DU and return to the installer. Proceed

with the OS X installation and follow the directions included with the installer.

4. If you are planning to sell or give your computer away, then do the following:

After you reformat your hard drive and reinstall OS X, the computer restarts to a

Welcome screen and asks you to choose a country or region. If you want to leave

the Mac in an out-of-box state, don't continue with the setup of your system. Instead,

press Command-Q to shut down the Mac. When the new owner turns on the Mac,

the Setup Assistant will guide them through the setup process.

Note: Portions of the above have been copied from What to do before selling or giving away your Mac - Apple Support.

What exact model do you have? To find the model identifier open System Profiler in the Utilities folder. It's displayed in the panel on the right.

You do not install using Disk Utility, but you need to use Disk Utility in order to repartition and reformat the HDD before you can install Snow Leopard.

See if you are able to do this:

Clean Install of Snow Leopard

1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

with your computer. Insert the disc into the optical drive and restart the computer.

After the chime press and hold down the "C" key. Release the key when you see

a small spinning gear appear below the dark gray Apple logo.

2. After the installer loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the Utilities menu.

After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive

size.) Click on the Partition tab in the DU main window. Set the number of

partitions to one (1) from the Partitions drop down menu, click on Options button

and select GUID, click on OK, then set the format type to MacOS Extended

(Journaled, if supported), then click on the Apply button.

3. When the formatting has completed quit DU and return to the installer. Proceed

with the OS X installation and follow the directions included with the installer.

4. When the installation has completed your computer will Restart into the Setup

Assistant. After you finish Setup Assistant will complete the installation after which

you will be running a fresh install of OS X. You can now begin the update process

by opening Software Update and installing all recommended updates to bring your

installation current.

5. If you are planning to sell or give your computer away, then do the following:

After you reformat your hard drive and reinstall OS X, the computer restarts to a

Welcome screen and asks you to choose a country or region. If you want to leave

the Mac in an out-of-box state, don't continue with the setup of your system. Instead,

press Command-Q to shut down the Mac. When the new owner turns on the Mac,

the Setup Assistant will guide them through the setup process.