Unable to enter BIOS - Lenovo G580 Laptop

Hi

I got a new Lenovo G580 laptop which did not come with any pre-installed OS. I installed Ubuntu in UEFI mode (I had not disabled UEFI/Secure Boot). Later I installed Windows 7. During installation it asked me to format the entire format as it did not recognize the GPT partition. Accordingly without thinking twice I erased the entire HDD and installed Windows 7. Now I am unable to enter into BIOS

Things I have tried:

1. Tried with F2, F1 and Delete keys while booting
2. Tried removing the battery and booting while pressing the above keys individually
3. Tried removing the battery and adapter, held the power button for 1 minute
4. Tried removing the battery and held the power button for 1 minute while the adapter was plugged in
5. Tried pressing F12 and going to the APP MENU but I can only see "Diagnostic Splash" Nothing else and in that diagnostic splash screen I see that the System BIOS is "shadowed"

How can i gain access to BIOS so I can disable UEFI and install Win 7 and Ubuntu side by side