How do you change the CMOS battery on the motherboard and restore the PC's settings please?

It's easy enough. Take the side cover off an you will see what looks like a watch battery about the size of a 20c coin. It is held in by a spring clip that you can push with a biro. Pop the new one in and look for the 'setup' option when you start your PC (F2 or Del usually). When in the setup program look around the options and choose the "load default or optimum settings". All cmos setup programs are different but the principle is the same.

Dear Aunty, that's great, and soooo easy. I have looked at the battery in situ and it is a Panasonic 3v CR2032. I don't suppose you know where I can lay my hands on one?
Thanks

Where abouts are you treefella?

Hi Jeni, Hondon de los Frailes. Loooong way from computer stores but trnsport no problema.
Chris