Thanks, I have ordered a new board.
Hi. The bios battery keeps going flat within 2 weeks. From what I have read it seems the motherboard is the most likely cause. When it was new it had a problem with the screen cable cable (when the screen was moved it would go blank) the guy turned up to fix it (in warranty) and replaced the mother board. That did not fix it and he had to return to replace the cable. I cant find a replacement board on Dells website and don't want to waste money on some cheap copy from aliexpress. is it worth fixing? where do I buy a replacement board? (will need to ship to NZ) This is the most expensive laptop we have bought an also the one that has caused the most trouble. Not sure I will buy Dell again.  
Bios battery keeps going flat.