Apple iMac (Early 2008) - Manual (Page 43)

Chapter 4 Problem, Meet Solution 43
Using Apple Hardware Test
You can use Apple Hardware Test to help determine if there is a problem with your
iMac hardware.
To use Apple Hardware Test:
1 Disconnect all external devices from your iMac except the keyboard and mouse.
If you have an Ethernet cable connected, disconnect it.
2 Restart your iMac while holding down the D key.
3 When the Apple Hardware Test chooser screen appears, select the language
appropriate for your location.
4 Press the Return key or click the right arrow button.
5 When the Apple Hardware Test main screen appears (after about 45 seconds), follow
the onscreen instructions.
6 Apple Hardware Test displays an error code if it detects a problem. Make a note of the
error code before pursuing support options. If Apple Hardware Test doesn’t detect a
hardware failure, the problem may be with your software.
For more information, see the Apple Hardware Test Read Me file on the Mac OS X
Install Disc 1.