ADB driver MK808 installed but ADB is not working
just use google usb driver in sdk/extra/google/usb_driver/android_winusb.inf 
you must add three lines in the file

;MK808B 
%SingleAdbInterface%        = USB_INSTALL, USB\VID_2207&amp;PID_0006&amp;MI_01
%CompositeAdbInterface%     = USB_INSTALL, USB\VID_2207&amp;PID_0006&amp;REV_0222&amp;MI_01

Then update the MK808B driver select from disk, use this file sdk/extra/google/usb_driver/android_winusb.inf then select first option is work fine for me.