Delete Ubuntu and fix windows boot

Step 1: Delete Ubuntu in windows
Right click on My Computer/ manage/ Disk management
Right click on Ubuntu disk/ Delete and format
Restart
Step 2: Fix Boot

Using Windows 8
Boot by boot cd or windows disk DVD
From command promt
attrib - s -h c:\boot\bcd - remove system and hidden attributes so it can be deleted.
del c:\boot\bcd - delete BCD
bcdboot c:\windows - re/create BCD

Using Windows 2000, Windows XP or Windows Server 2003 CD:

Boot using setup disc and enter into "Recovery Console" by pressing "R" key, select your Windows installation and enter Administrator password. If you don't have any password, press Enter key. Now run following command:

fixmbr

Press "Y" to confirm and type Exit to exit from recovery console.

Using Windows 98 CD:

Boot into Command Prompt and run following command:

fdisk /MBR

Exit from command prompt by typing Exit and press Enter.Reference