Open the Command Prompt, then type bootrec /fixmbr into the Command Prompt. Click 'Repair your computer' and you should see a screen like the first image. You should see this on an installation media. You should see this or a similar screen on a recovery media. Grab a Windows recovery or installation media and boot from it. Windows will only install as an evaluation copy for 30 days without a genuine product key. If you don't have a Windows recovery or installation media, you can download official ISO files for Windows 10, Windows 8, or Windows 7 from the Microsoft Download Center and burn them on a DVD or a USB drive. Using Windows Recovery or Installation Media If you have a newer Dell laptop (such as the Dell Inspiron), you would need to do so by changing the boot sequence in the UEFI settings, which will be discussed later.
The first step can be done with a Windows Recovery DVD/Installation DVD or a Ubuntu Live DVD.
Then, you would need to remove the Ubuntu partitions. To remove Ubuntu from a Ubuntu/Windows dual boot system, you will first need to replace the GRUB bootloader with the Windows bootloader. If you have a single-boot system with only Ubuntu installed, you can install Windows directly and override Ubuntu completely.
