James McC :
This is a desktop computer and we will be changing the board at home. I also have a usb 500g backup drive on the system. The system works between periods of shutting down
Ah. Sorry. My pavilion is a laptop, so my first thought. You WILL need to reinstall windows unless you get the same model board. If you get the same model it will just work. If its the same chipset it *might*.
if its not the same board the problem is you wont have disks and the original restore disks wont work on a new board. However, you can download the official ISOs here.
Http://en.community.dell.com/support-forums/software-os/w/microsoft_os/3316.2-1-microsoft-windows-7-official-iso-download-links-digital-river.aspx
There are installation instructions, simply select the correct version that matches your LEGAL product key and certificate of authenticity that is attached to your machine. This is perfectly legal, your OEM license allows you to replace the motherboard if it fails, but you will have to call Microsoft when you activate it, instead of doing it online. Shouldn't be any problems
After you install windows you'll need to install the motherboard.and other hardware drivers, and any programs, and restore your Data. Drivers will be on the board manufactures website, programs that came preinstalled, and still apply, say a DVD player or something, you should be able to get from HPs website.
If you bought programs you can get the product keys out of the registry before reinstalling windows so you can reinstall them. Software MUST be reinstalled or it wont work. You can't just copy it back. You can only copy the Data back