Eliminate W7 from Dual Boot and Keep W8

My system has 3 HDD's, Disc 0 contains a partition containing W7 and all of My Documents. Disc 0 also has a partition that contains W8.1.

Disc 1 is used only for backups and images
.
Disc 2 is currently empty.

I want to restore an image of W8 to Disc2 and eliminate W7 and W8 from Disc 0 while keeping the My Documents folder from W7 on Disc 0. Can I just delete all of the W7 folders except the My Documents folder? Or should I make a backup of the My Documents folder and then just format Disc 0?

When I'm all done I'd like to have W8.1 on the current Disc 2, My Documents and all data on the current Disc 0 and continue to use Disc 1 for backups.

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