Hi,
moving the C drive in the why that you want is not a good idea. I know it would be nice and easy and you could do that, but it will most probably cause you lots of problems and no end of grief.
The first big issue would be that your new Gigabyte board will need to have its own drivers installed.
Because you are re-configuring your other PC components, Windows could well need to be re-activated as it is possible it may deem you are trying to install it onto a 2nd machine.
When replacing a major component, like your motherboard, it is always best to start over and re-install everything. If there are any problems it is easier to check back, if an error occurs, as you will know what the last driver or piece of software was that you installed.