How can I reset CMOS or BIOS settings?

If your computer is having issues booting, has errors during boot, running into issues after adding hardware, or you're having other abnormal system behaviors that cannot be resolved though any other method, it may be necessary to reset the CMOS settings or load the default or fail-safe defaults as explained below.

Note: If you are seeing an error about a "media test failure", there may be a loose cable inside the computer, or the hard drive might be bad.

Load or Reset defaults

  1. CMOS restore defaultsEnter CMOS setup.
  2. In CMOS setup, look for an option to reset the CMOS values to the default setting or an option to load the fail-safe defaults. With many CMOS setup screens, there will be a function key to do this. For example, the F5, F6, F9, F11, or F12 key, as shown in the picture, may be set up as a shortcut to load the default settings. Other setups may list an option that you can arrow over to using the arrow keys and pressing Enter.
  3. When found and selected, you'll likely be asked if you're sure you want to load the defaults. Press Y for yes or arrow to the yes option.
  4. Once the default values have been set, make sure to Save and Exit and not just exit.

Reset Configuration Data

In addition to restoring the system defaults, if you've recently added new hardware or resetting the default values did not help resolve your boot issues, you may also want to reset the configuration data.

Note: Not all CMOS setup screens have this feature.

Under advanced

If you're working on a computer with a Phoenix BIOS that has Main - Advanced - Security - ... across the top of the screen, you can get to this setting by using the right arrow to move over to Advanced. Under Advanced, arrow down to the Reset Configuration Data option and change the value from Disabled or No to Enabled or Yes.

Once the above has been done, press the F10 key and Save and Exit CMOS setup.

In PnP/PCI Configurations

If you're working with a Phoenix BIOS that has different options and one of them is PnP/PCI Configuration, move the cursor down to this option and press Enter. Within the PnP/PCI Configurations, change the Reset Configuration Data from Disabled to Enabled.

Once the above has been done press the F10 key and Save and Exit CMOS setup.

Hard reset the CMOS

Caution: When inside your computer, make sure you're aware of ESD and all it's potential dangers.

CMOS batteryIf the above steps do not reset the CMOS settings, we suggest removing the CMOS battery, like the one in the picture, causing the computer to forget all CMOS settings, including the password. Wait 5 minutes after removing the battery, then put the battery back into the motherboard and turn it on.

If your computer does not have a CMOS battery or you're unable to find it, you'll need to do a hard reset on the CMOS using a jumper or dip switch on the motherboard. Information on finding these can be found in your computer or motherboard documentation.

Additional information

  • See the BIOS and CMOS definitions for further information and related links.