Turning internal hd back to external

A while back I turned an external hd into a internal hd when my main hd went out on me and I didn't want to buy a new one when I had a drive available. I have a new PC on the way and I would like to go back to using the drive as a external, but it now has windows 7 installed on it. Can I turn the hd back into a external without removing windows and still be able to access all my files without having to boot into windows off the hd? Or will I have to backup all the files I want off the drive and reformat before using it as an external again?
 
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