This what i did which made things to mess up.
1)I installed Windows 8.1
2)I installed ubuntu 15.04 in different partition
3)I upgraded windows to windows 10
4)I upgraded ubuntu to ubuntu 15.10
5)Thought to reinstall ubuntu so tried to replace existing ubuntu partition with new ubuntu using usb stick, but when i tried to reintsall using usb it used show an error like: GNU GRUB Version 2.02~ beta 2-9
Minimal BASH-like line editing is supported. For the first word, TAB lists possible command completions. Anywhere else TAB lists possible device or file completions.
6)Trying to get rid of this i deleted the ubuntu partition
7)Got stuck in grub rescue mode
8)Now again to set things right i connected a live usb and installed ubuntu
9)Now grub is not recognizing Windows 10
Help me get out of this, I have some important files in windows 10.