Usually straight forward procedure. Most models the Cmos battery is excessible once inside the PC you will find it usually on the Motherboard. Remove all connections to the PC including the mains lead. Push the on off switch which you push when starting the PC to make sure that any power still inside the system after switch off has been fully exhausted. Remove the enclosure so that you have easy access to the motherboard. Carefully price out the battery and replace. Once new battery is installed reconnect all leads and start PC depending on model this might take a time for the Bios to recognise the change once it does your clock should be automatically be reset. Do not rush this process let your PC have the time it needs to recognise this change.
Carlito Corway, May 2008
