The BIOS on an OptiPlex 755 can allow you to configure various aspects about the way your computer's hardware functions. The BIOS does not handle your computer's software--that is all managed within the Windows operating system. If you want to access the BIOS on your OptiPlex 755 computer, you need to know which keyboard key to press at which moment during the computer's startup.
Turn on your Dell OptiPlex 755.
Wait to see the "Dell" logo appear on screen.
Press the "F2" keyboard key to load the BIOS on your OptiPlex 755.