To remove Ubuntu, you will need a Windows Recovery DVD or Installation DVD, or a Ubuntu Live DVD.
Note: If you don't have a Windows Recovery or Installation DVD, you can download official ISO files for Windows 10, Windows 8, or Windows 7 from the Microsoft Download Center. Windows will only install as an evaluation copy for 30 days without a genuine product key.
Using a Windows Recovery DVD or Installation DVD
Grab a Windows recovery media or installation CD and boot from it. You should see this or a similar screen on a recovery media CD.
You should see this on an installation media CD. Click "Repair your computer" and you should see a screen like the first image.
Open the Command Prompt, then type
bootrec /fixmbr into the Command Prompt.
Reboot and boot into Windows. Then follow the steps below to remove the Ubuntu partitions.
Using a Ubuntu Live DVD and Boot Repair
If you don't have a Windows recovery CD or you are constrained to download and burn the ISO files mentioned before, you can use Boot-repair. It is a tool that fixes most boot problems(Windows or Ubuntu). I suggest using a Windows CD if possible.
Boot from a Ubuntu Live DVD or USB
Type these lines in the terminal one line at a time.
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install boot-repair
Search for Boot-Repair in the Dash and launch it.
To fix your computer with Boot-repair, simply click the "Recommended Repair" button. Then follow the steps below to remove the Ubuntu Partitions.
Deleting Ubuntu Partitions
Go to Start, right click Computer, then select Manage. Then select Disk Management from the sidebar.
Right-click your Ubuntu partitions and select "Delete". Check before you delete!
Then, right-click the partition that is on the Left of the free space. Select "Extend Volume". Go through the Wizard and Finish it.
Note from Tanner: If you are using an extended partition, you might have to remove the big extended partition to make the space unallocated.