I need urgent help. I recently finished building my gaming PC, so I brought Windows 8.1 for my OS. I stuck in the x64 bit DVD and waited. It was on "Preparing files for installation" all of a sudden, my power goes off. I turn the PC on and start the DVD again, and after choosing the install option, it says that the partition of the HDD is not available to install on, so I format it with the option. I accidentally then delete it. Now I brought a new HDD after realising that the current one was damaged, and now the product key doesn't work. Do I purchase Windows again, or can I get around this?