My parents were on vacation last weekend and franticly called me saying that they couldn't get their Inspiron 1501 to boot anymore without the BIOS whining about the battery. Before this happened, they said the "battery went dead with negligible pre-warning".
On bootup, the computer says:
WARNING: The battery cannot be identified.
This system will be unable to charge this battery.
With options to enter the BIOS or continue booting.
I got to look at the machine last night. The battery still holds a charge, and will recharge. Windows detects it as a DellPY9617 battery manufactured by "DynaPack". I didn't get the BIOS revision, but the machine's ship date was 7/21/2007.
The recommendations I could find on the internet varied from "discharge the battery completely" to "your computer is too old" to "update the BIOS", and wanted a more specific answer before doing something drastic.