Seeing as your Motherboard is faulty
, the biggest hurdle is likely to be the chipset drivers. These inform the system how to interact with your devices.
Yes, make sure you back up your drive - remember even if you have just one Hard Drive in Windows 7 you can shrink it, create a new partition and then move your docs, important files, etc., to it (including ones you may need on reboot, like chipest drivers) - [note
: if you decide to re-install, make sure you do not affect the partition with your important files on it
So: The last thing you shall do before shutting off your system and powering down prior to replacing the faulty motherboard
is: Uninstall your chipset drivers.
After changing motherboards, make sure you enter the BIOS on FIRST boot (make sure)
, check that your Hard Drive(s) are detected, make any other required changes to the BIOS, and reboot once more, then going to the OS. The next thing to do is to install your new chipset drivers.
If you cannot boot, use startup repair from your DVD.
If you get a new activation request make sure you inform them that your Motherboard was faulty and is now on it's way to be recycled.
I also recommend at least re-installing (forcing) your video and sound drivers after the new chipest drivers are installed.
BTW, MS can decide at their discretion whether or not to allow a new PID. In all likelyhood a change from say an Intel single core cpu/mobo to a multicore AMD one or even from a Socket 478 to an i7 may cause a stir...