Motherboard change. Need help with OS

Hardware Motherboards
1

Hi!

I'm change my motherboard from a acer FRX780M to a Asus sabertooth 990FX r2.0.
How do i reinstall my OS with only the product key? I didn't get a cd with my computer because the OS was pre-installed.

Hope you can help me!

Thank you!

2

well you aquire a windows install by means that may or may not be ilegal and then use the product key to make it legal

Hope it helped! 

3

So if i can get a iso file for windows 7. I can just use the product key to make it legal?

4

Get the windows 7 install files from "the bay" and then use the product key to activate it.

5

ok, thanks!