Replacing Image stored on Hidden partition

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Hi-

I know there is a way to backup to factory settings on the hidden partition but what I wanted to know (since I have the recovery cds) is if I can replace that image with a more recent one from time to time. I know I can add a partition but I don't want to keep on using more and more HD space but I do want it available to me always. Does anyone know how to do this? I hope I explained it ok. Thanks!

-Dan