Whenever I start my computer it says my computer case is opening.What does this mean?

Its a Windows XP and I really dont know alot about this stuff.Whenever I start my computer it says my computer case is opening.What does this mean?
The BIOS on most motherboards has a setting to detect case open. This is rarely used, and should be disabled. Try pressing F2 or del, depends on the board, during boot to get to BIOS settings and look for a case open setting. Turn it off. Do NOT change anything else.Whenever I start my computer it says my computer case is opening.What does this mean?
It probably means someone has tampered with the ';tower'; of your pc. Maybe you did it by accident, just look to make sure none of the sides of your tower ';the box where you turn on your pc'; arent disconnected. With newer computers, they have this built in to help people realize their computer is open