Boot camp windows installation problem

Hi... I have just bought a Macbook pro I7, 512ssd, 16 Gb RAM and double graphics card.

I tried installing windows 7 first and 8.1 after with boot camp without success.

What happens is that towards the end of the installation process it says it cannot modify/write to the boot record.

When I reset the machine and hold the option button it keeps giving the "windows" option even after I erased the boot camp partition.

I've tried to create a new partition and then erasing it in the hopes that the boot record would be modified by disk utility: no result.

In other words the windows/boot camp partition is gone but it still shows when I press the option button.

How do I get rid of it for good? The thing itself would not bother me much but I suspect that that is the reason why windows shows the above error...

I've tried repairing with disk utility but again no result. Thank you...