Q: how to restore to factory settings

You would use your original 10.2 or 10.3 Install disks that came with th eMac.

Insert your Install disk 1 into the drive and then Restart, and hold down the C key to take you to the installation windows.

Select your language, the start up Volume and choose Erase and Install.

At the point your registration process starts, abandon the registration, quit and eject the disk and switch of the computer.

This will allow the new user a freshly installed system, whereby they can complete the registration process themselves. Make sure you hand on the disks.

What if you dont have the install disks?

bagel77 wrote:

 

What if you dont have the install disks?

Then you cannot restore to factory settings, nor can you run Repair Disk operations on the Hard drive, and some other technical matters like resetting the Admin password, (though that can be accomplished by other means), so it is important for a Mac computer to have its disks, but generally when old Macs are exchanged the seller forgets to hand on the disk to the new owner.

Acquiring a replacement set of disks is usually not cost effective. In fact on the secondhand market, a set of old Mac disks are probably worth more than the  computer it came with. This effect may be lessening now as even that old software is itself getting a bit long in the tooth.