You may be right but since this is the BIOS showing this message that's grim news. Repair will exceed replacement costs so let's try the usual before we write it off.
1. Install the BIOS version that the machine came with.
2. I bet you pulled the battery out and cleaned the contacts. But just so I don't forget to add this item I put it in the post.
3. The batteries are ONE YEAR devices. Proof is the 300 Cycle Rating.
4. In this forum there is a sticky or top post with a note about battery detection in Windows. I re-read your post and maybe it was in Windows? Can't tell.
Hope this gives you a few ideas.
When I turn it on I get a message that says something like 'cannot detect battery, press any key to continue'.
After I press any key it will then start up as normal.
The battery will no longer charge at all so I can only use the laptop when plugged in. It shows 0% charge on the battery status in case there was any doubt that it is not charged!
The laptop is around 3 years old and it is the original battery. I only use the Dell charger it came with. I know batteries are not made to last much longer than 3 years and I expected battery life to be reduced dramatically but not for it to die completely. But the fact that the computer is saying it can't detect the battery suggests to me that maybe the problem is not that the battery is dead?
Any advice much appreciated!