Dell OptiPlex 990 (Early 2011) - Manual (Page 73)

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Problem Description Memory modules are detected, but a memory configuration or
compatibility error has occurred.
Troubleshooting Steps
• Ensure that no special requirements for memory
module/connector placement exist.
• Ensure that the memory you are using is supported
by your computer.
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Problem Description A possible expansion card failure has occurred.
Troubleshooting
Steps
• Determine if a conflict exists by removing an
expansion card (not a graphics card) and restarting
the computer.
• If the problem persists, reinstall the card you
removed, then remove a different card and restart the
computer.
• Repeat this process for each expansion card installed.
If the computer starts normally, troubleshoot the last
card removed from the computer for resource
conflicts.
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