Help with Getting info off old hard drive..

I need to get all my freinds important files off his old hard drive B4 I reinstall windows. Here is what makes it difficult, his motherboard went bad, so i am installing a new motherboard, cpu, and ram. and the same hard drive. Here is what i plan to do= i am going to install a spare drive that i have and install windows and set the drive i need to get the data off of as the slave. Is this possible to do?

Connect his old HDD to your SYSTEM, back off all of the needed data.
Then you don't need to worry about losing data.

You can reinstall Windows in a non-destructive manner, but this could leave you with multiple Windows directories and lots of duplication of stuff. I think it would be cleaner to be able to wipe a clean install.