Dell OptiPlex 990 (Early 2011) - Manual (Page 70)

• If available, install working memory of the same type
into your computer.
LED
Power Button
Problem Description A possible hard drive failure has occurred.
Troubleshooting Steps Re-seat all power and data cables.
LED
Power Button
Problem Description A possible USB failure has occurred.
Troubleshooting Steps Re-install all USB devices and check all cable
connections.
LED
Power Button
Problem Description No memory modules are detected.
Troubleshooting
Steps
• If two or more memory modules are installed,
remove the modules, then reinstall one module and
restart the computer. If the computer starts
normally, continue to install additional memory
modules (one at a time) until you have identified a
faulty module or reinstalled all modules without
error.
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