It sounds as if either the bios has been corupted. To cure: Check manual for location of BIOS reset (3 pins-1 jumper covering either the first 2 or the second 2) and clear bios.  You need a new battery. Check manual for battery type and contact maplins click here or your local computer shop to get a new one. [If you canot find the type / number, remove the battery and tae it with you. REMEMBER:: You must earth yourself, and preferably use a anti-static wrist strap before touching the inside of your computer. Don't forget it must be Unplugged first.