Windows 7: BIOS ACPI not complaint, this errror come, Solution please !

hey , i tried to install windows 7 ultimate , windows 7 professional on my laptop , but always after installation this error comes up:
"
A problem has been detected and Windows has been shut down to prevent damage to your computer.



If this is the first time you've seen this Stop error screen restart your computer. If this screen appears again, follow these steps:

The BIOS in this system is not fully ACPI compliant. Please contact your system vendor for an updated BIOS.

Technical information:

*** STOP: 0x000000A5 ............................................... "

my laptop is dell inspiron n4050 , before this the windows 7 had installed but now it is not , i tried to install 7 to 8 times but always this error comes up , i haven't even changed any hardware . then why this error comes, ? i even clean installed , and tried all the versions of windows 7 , ultimate and professional.
please tell me the solution ,

any help ??

ok , the exact error is: The BIOS in this system is not fully ACPI compliant. Please contact your system vendor for an updated BIOS.

Technical information:

*** STOP: 0x000000A5( 00000013 x 00000005 x 00000000 x 00000000)

PLEASE HELP URGENT !!