I just had a thought, since i already have my games like BF3 waiting, that maybe I could use my HDD with the OS Win 7 on it, along with my current ram, with my new mobo and other parts to hold me over until i finish it.. And if everything IS compatible, if there is anything special id have to do to make my current ram and OS work with the new parts. (temporarily of course, to where i could switch the hdd and ram back to my current computer later..
As long as your old ram is DDR3 like listed in the specs you linked, you should be able to use that.
I don't know about the old OS already installed on the old HDD. It might boot up in safe mode maybe so you could start removing old drivers/install new drivers. If you reinstalled fresh from disk it should work until activation starts complaining.
Either way, I have to point out that the MS OEM license agreement does not allow installation of that copy on another machine so I'm not recommending it. Of course you make your own decision on this since your situation is temporary. Alternatively, you could also try one of the free linux distributions for kicks.