Your success may vary.
I replaced my son's failed X58 based motherboard with a H61. I was prepared to do a clean install, but decided to try booting from his windows 7 hard drive.
It worked well enough, and all I really needed to do was to install the chipset drivers which came with the motherboard cd.
Plan B was to boot from the windows 7 dvd and try to do a repair install.
If you were to attempt this, clone the original drive, or protect it so you can recover if the repair install fails.
Plan C was a clean install, which would require apps to be reinstalled.
In your case, I would not be certain that other parts besides the motherboard were not damaged also.
I know that reinstalling apps is a pain, but considering the age of the pc, perhaps it might be time to update the components.
If you get a small ssd for the os, it will make it a very snappy machine.