Windows – BIOS not ACPI compliant, on windows 7 installation

I was facing a problem of blank screen with cursor after login in my Lenovo G40-30 laptop which was pre-installed with windows 8. So to resolve it I somehow decided to change it from UEFI boot to legacy boot After that I am not able to access boot options from any key F2/F12. Then I tried to install windows 7 from a bootable usb pen drive, which I created from Rufus software with option 'Partition Scheme and Target System type' set as 'MBR partition scheme for BIOS or UEFI'. The laptop now boots with pen drive, and starts installing windows, but shows error BIOS not fully ACPI compliant, with error code 0x000000A5. Why I am getting this error, and how to resolve it?