since yesterday i'm stuck with the dual boot. I can't see Windows 8.1 in the menu. The problem started when I removed Ubuntu from the windows disk manager, so I reinstalled it for solving it. Now I have that error, tried to solve with boot repair without success (http://www.paste2.org/87V4MBXY)
use "boot-repair disk" google it. It is live CD about 600mb. Mandatory condition is it should be connected with WiFi before repairing boot loader.It will automatically scan your all bootable drives and will give you instructions on the spot. A menu will come where mouse will not work. In that condition you have to use tab to move courser and space to select.