Selling my iMac G5 but want to delete all my documents first

Question

I have bought a new intel iMac & will sell my old iMac G5 on eBay. I want to restore it to its original software making sure that all my personal stuff is erased permanently. What is the correct way to do it?

Answer 1

Miriam's suggestion is excellent.
When I part with a Mac I take it a step further. I suggest selecting the Security Options (Disk Utility) and choosing the 7-times write over option. There's also a 35x option.
Here's the Disk Utility Help page for "Security Options":
You can securely erase a disk to make sure the confidential information it contains cannot be recovered.
Usually when erasing a disk, Disk Utility does not erase the files' data. It erases just the information used to access the files. Many commonly available disk recovery applications can easily recover that data. When securely erasing a disk, Disk Utility writes over the erased files' data, so it can never be recovered. You can choose to write over the data once, 7 times, or 35 times. Writing data over the disk 7 or 35 times is more secure than writing over it once, but takes longer.
In Disk Utility, select the disk you want to erase and click Erase.
Specify a volume format and name for the disk.
Click Security Options and choose to write over the disk once, 7 times, or 35 times. Click OK.
Click Erase.
Writing data over the disk 7 times meets the U.S. Department of Defense (DoD) 5220-22-M standard for securely erasing magnetic media.
If you select your startup disk, the buttons are dimmed because you can't erase your startup disk. To erase your computer's startup disk, you must start up from another disk, such as your Mac OS X Install disc.