Hello,
 while testing kernel 2.6.22.1-20.fc7 on Fedora 7 x86_64on my Dell 
Inspiron 1501 with the latest available BIOS version 2.4.1, I jumped 
into this:

ACPI: System BIOS is requesting _OSI(Linux)
ACPI: Please test with "acpi_osi=!Linux"
Please send dmidecode to linux-acpi@vger.kernel.org

Adding acpi_osi=!Linux to the kenrel command line didn't change 
anything, so here I send the output of dmesg and dmidecode, I'm 
available for any further request or testing.

Dario