Yeah im going to try the cmos battery, the orginal battery is 6 yrs old now. I bought one this morning if it dont work i got a bios flash disk to try, if that dont work the new cr2032 battery is coming out and going into my door bell (that dont work either at the moment ) and the pc can rot in the loft lol.

Strange it should go while the PC was on and working fine tho.