Problem at boot. i have a dsktop maxdata with asus p4b mother board,my problem is the following

Question

i have a dsktop maxdata with asus p4b mother board,my problem is the following message displayed at the booting, it enters setup bios with displaying the following message:

message confirmation
te system intruded,chassis opened
or tempered before.please check
the system.
ok

after cheking the bios all seems correct and reboot machine the same thing happens indefnitly.
thank you to help me