Easiest way to return to stock?

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http://forum.xda-developers.com – Bought my Nexus 7 tablet and just don't use it as much as I thought I would being I have a Android phone also so I'm thinking I will return it to stock and get a laptop. Problem is I tried using CWM and the factory reset to erase it but neither do anything. I do have it rooted and unlocked. (HowTos)