After you remove and replace the cover on some Dell computers, the following message is displayed at the next system start-up:ALERT! Cover was previously removed.
Some Dell computers have a chassis intrusion switch will detects when the cover has been removed. This acts as a security measure against hardware tampering.
Resolution-Technicians and Advanced Users ONLY!
To reset the chassis intrusion detector, enter System Setup (BIOS settings), select System Security, and reset Chassis Intrusion to Enabled or Enabled-Silent.