I have a Toshiba C55t-A5370 Laptop. I ran AVG PC Tune up on it and it killed it. I mean it did a total hard drive wipe out on it. Even the hidden partition was gone. It had Windows 8.1 on it and a friend put Windows 7 pro on it because he had the disk for it. It's alright but I'm not crazy about it. I downloaded the Windows 8.1 upgrade onto a flash drive but am not sure how to go about putting onto my laptop. Help please?