Booting From An OS X Installer Disc
1. Insert OS X Installer Disc into the optical drive.
2. Restart the computer.
3. Immediately after the chime press and hold down the "C" key.
4. Release the key when the spinning gear below the dark gray Apple logo
5. Wait for installer to finish loading.
Boot Using OPTION key:
1. Restart the computer.
2. Immediately after the chime press and hold down the "OPTION" key.
3. Release the key when the boot manager appears.
4. Select the desired disk icon from which you want to boot.
5. Click on the arrow button below the icon.
Are you sure her computer can even be started from an old Leopard DVD?
Holding down the "c" key will boot from disc (DVD). If she holds down the "option" key, she will have the option of selecting which disk or disc she wants to boot up from.
You do not indicate which OS your daughter has. Am I assuming correctly that it's Leopard since that is the disc you are sending her? If you or your daughter have the DVDs that originally came w/the computer that is the one she should be booting up from.
Shut down your computer and disconnect all peripherals (keyboard & mouse if pertinent) from your computer. Now reboot.
If the Mac starts up normally, shut it down again and then plug in one of the peripherals (keyboard or mouse first) and start up your computer again. If it does so successfully repeat the process, adding one peripheral at a time until your Mac acts up. At that point, disconnect the last peripheral you added, reboot your Mac and search the peripheral vendor's website for an updated driver.
If no driver exists or the problem remain after installing the new driver, try a different cable or a different port on your Mac.
If none of the above works, again disconnect all peripherals from your Mac, hold down the "shift" key to start up in "Safe Boot" mode.
If the Mac starts up correctly, restart without pressing the "shift" key.
If your computer still does not start up properly, shut it down and restart it while holding down the Apple+Option-P-R keys; keep holding "all 4 keys" down until you hear the startup sound "twice."
If none of the above work Disconnect all peripherals from your computer. Boot from your install disc & run Repair Disk from the utility menu. To use the Install Mac OS X disc, insert the disc, and restart your computer while holding down the C key as it starts up.
Select your language.
Once on the desktop, select Utility in the menu bar.
Select Disk Utility.
Select the disk or volume in the list of disks and volumes, and then click First Aid.
Click Repair Disk.
(If Disk Utility cannot repair, you will need a stronger utility (3rd party) - Diskwarrior or Techtool PRO)
Restart your computer when done.
Repair permissions after you reach the desktop-http://docs.info.apple.com/article.html?artnum=25751 and restart your computer.
Remove any 3rd party ram.
Reinstall Snow Leopard - This will install a "fresh" copy of Snow Leopard without archiving old system files but leaves the rest of your files in place.
If your computer is still under warranty or you have Apple Care, take full advantage of it by letting tech support deal with your problems. It's what you're paying them for.
Out of warranty - take the computer to an Apple store or an AASP. Whichever is more convenient for you.