boot...

place dvd in drive.

hold down the c key power on machine.  continue holding down c key until machine is booting.

hold down the option ( also know as the control ) key then power on machine.  continue holding down option key until startup manager appears. click on dvd icon.  click on large right arrow.

Robert

Format a disk using the installation DVD

How to run disk utility from your startup DVD.

1. Insert your  startup DVD  into your reader.  Power down your machine.  Hold down to the c key.  Power on your machine.  This will bootup your startup DVD. ( Alternatively, you may hold down the control key, this brings up the startup manager. Click on the desired volume. Click on the right arrow. )
2. This will bring you to a panel asking you for your language.  Pick your language.
3. 
   
   
4. You you come to the Install Mac OS panel.  Do not install.
5. 
6. Click on the disk utility.
7. Start up disk utility.
   On the left pane view, you will see a list of all your disks.  Click on the external  disk.
   Click on the partition tab.
   

   

   
   
   
8. You will now see how your external disk is currently set up.  Fill in the information as appropriate. You should pick Mac OS Extended (Journaled).

Additional information

More details on formatting.
http://www.kenstone.net/fcp_homepage/partitioning_tiger.html

To format  the startup drive, you will need to run disk utility from your installation DVD.

This article  will tell you how to get to disk utility.  Once in a disk utility, you can go and format the disk.

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

To format your startup drive, you will need to run disk utility from your startup DVD.
Mac OS X 10.4: About the utilities available on the Mac OS X 10.4 Install DVD

http://support.apple.com/kb/HT2055

There are two common ways of boot an installation dvd.

Use of the c key or use of the option key.  I like to use the opiton key.

Try this:

  Start with DVD in drive. Power off your machine. Hold down the option key when you poweron. This will bring up the startup manager. Click on cd/dvd. Click on right arrow. ( I think that this is your best approach. )

Your statup manager may be slightly different, but this is the idea.

http://docs.info.apple.com/article.html?artnum=106178

Apple will say poweron then quickly hold down option key.  How quick to you need to be?  I found that holding down option key then powering on works. Wait until startup manager appears.

Robert

Is the drive showing up in Disk Utility?

If you're a Widows PC guy, you might not automatically know this, so let me add a step to the post above.  The image under step 7 is of the Partition tab in Disk Utility.  Do you see the "Option" button near the bottom of the window?  You need to click on that and select "Apple Partition Map" (Not GUID, not Master Boot Record).  PowerPC Macs require the Apple Partition Map for their boot drives.  Then go to step 8 and format to Mac OS Extended (Journaled).

If the drive isn't showing Disk Utility, then we have other issues.

if hes trying to install a 2TB drive (which i assume is a sata 6), the G5 won't see it.

You need to jumper the pins on the drive to downclock the sata speed so the G5 can recognize it.