ACPI error when trying to install Windows Vista RC1 on a 5150

I have a Inspiron 5150 desktop pc. It currently has XP Home installed.

When I try to upgrade the OS to Vista RC1, I get a error message that reads:
"This computer is not compliant with the Advanced Configuration and Power Interface (ACPI) standard. Windows must be installed onto a computer that supports ACPI. Contact your computer manufacturer for a BIOS update or install Windows on an ACPI-compliant computer."

I have downloaded the latest BIOS update that I could find (A05).

I would prefer to do/try an OS upgrade versus a clean install.
Any suggestions for the ACPI message and a work around?

Thanks,

Rog