The numbered lights on the front panel of the computer are used to diagnose problems with the startup process. They are numbered as 1, 2, 3, and 4. (Figure 1)

Figure 1 - 1234 Diagnostic LEDs

	Note:
	On Dell® XPS® computers, the diagnostic LED lights are located behind the small door that also covers various input and output jacks.

If the main power button LED on the computer is solid green, but the numbered diagnostic LED lights are on in a specific sequence, there may be a problem with something inside the computer. This article will help resolve the problem without opening the case.

If the main power button LED is flashing or solid yellow, this could indicate a hardware problem that is beyond the scope of this article.

Disconnect any devices from the computer except for the keyboard and monitor. You may temporarily disconnect devices such as the following:

• Mouse
• Printer
• Headset
• Memory key
• Any USB-connected device

This should help eliminate any external device as the source of the problem. If disconnecting a particular device allows the computer to start up without an error, that particular device will need to be examined.

Plug the computer back into a power outlet that you know works properly with other electrical devices.

	Note:
	Be sure to bypass any surge protectors or Uninterruptible Power Supply (UPS) units temporarily. If the computer functions properly when connected directly to the wall outlet, consider purchasing a replacement surge protector or UPS.

Power the computer on and check to see if the diagnostic LEDs still indicate an error.

Try the keyboard in a different USB port to eliminate the USB port as a source of the problem.

Also, if you have a spare USB keyboard, try connecting that keyboard to the computer instead. If the other keyboard allows the system to boot, it is likely that the first keyboard has a problem.

Additional troubleshooting of this problem will require intermediate to advanced knowledge of the inside of a computer. Refer to the Dell troubleshooting Wizard to troubleshoot this issue further:

"Front Quad Pack Diagnostics Light-Emitting Diodes (LEDs) [ Dell™ Dimension™, OptiPlex™, and XPS™ systems ]" Wizard ID: 286725.

1. Browse to the Dell Support Website.
   
   
2. Under Who Do You Need to Contact?, click the More Details link that appears below Contact Technical Support.
   
   
3. Click one of the following options that appear under Contact Dell:
   
   
   • Chat Online with Technical Support
     Use this option to start an online chat session with a Dell Technical Support representative.
     
     
   • Call Technical Support
     Use this option to obtain a telephone number for Dell Technical Support.
     
     
   • E-mail Technical Support
     Use this option to send an e-mail message to Dell Technical Support.
     

	Note:
	When contacting Dell Technical Support, please have the product information and Service Tag number available.