Question about upgrading Windows 7 to Windows 8.

Hello there!

I have Windows 7 installed on my laptop but it is pirated. I managed to pass the genuine process and I don't have any problems regarding the activation. It appears genuine so to speak. Now i decided to upgrade to Windows 8 for 29 €. Is that possible? Has anyone done upgrading pirated Windows 7 to the 29 € Windows 8 and are there any problems with the activation later? I'm concerned that Windows 8 would not install on top of my current Windows 7 if it detects that it is not officially genuine.

And one more thing. Would I be able to install Windows 8 from the upgrade I'm going to buy if I format the whole hard drive and I don't have any OS on the laptop?

Thanks in advance!