When I got home from school I booted up my PC and found an error message. I cannot access my desktop. My PC was working fine last night and I have not made any driver changes recently. My PC is custom built and I'm using windows 8.1. As soon as I turn on my PC I see a message that reads, "your PC needs to be repaired. The boot configuration data for your PC is missing or contains errors. File:\EFI\Microsoft\Boot\BCD Error code: 0xc000000f. You'll need to use the recovery tools on your installation media..." It also says I can press esc for UEFI firmware settings. Not to mention I do not have a cd copy of windows 8.1. The guy who built my PC gave me a download code. What should I do?