i'm planning on getting an asus M5A99FX motherboard along with an FX-8350 to replace my current A10-5700, however it has come to my attention that i will need to either repair or reinstall my os. the computer i'm upgrading was a prebuilt system, so i don't actually have a product key or disk for windows 8.1 so i'm wondering if there are any ways to complete this upgrade without having to buy a new copy of windows to install