Windows doesn't recognize Nexus 7 in recovery mode So I have the Nexus 7 (2012). When the tablet is on and USB debugging is enabled, ADB recognizes it. But when I shut it off and put it into recovery mode, then press power and volume up to sideload, Windows/ADB does not recognize it. If I navigate to usb_driver it says it can't find a driver there. I'm trying to update it to KitKat using the OTA update.
The problem is that you're missing the adb recovery driver. You might consider trying Koush's universal USB driver installer -- it solved this very problem by installing the missing drivers.