How to Delete a Second Installation of Windows

1. Turn on your computer and boot to the Microsoft Windows operating system that you wish to keep on your computer.
2. Open 'My Computer' and navigate to the Windows folder containing the Windows installation that you wish to delete. If you are unsure which folder contains that installation, go to the Start menu, click 'Run', and type in '%windir%'. The Windows folder of your current installation will appear, so now just find the other Windows folder.
3. Delete the other Windows folder. This can be done by selecting it and clicking the 'Delete' key on your keyboard, or by right-clicking the folder and selecting 'Delete' from the menu.
4. Right-click on 'My Computer' and select 'Properties'. Now that you've physically removed the Windows installation files, you need to tell your computer to stop looking for them on boot-up.
5. Click the 'Advanced' tab, then click the 'Settings' button in the 'Startup and Recovery' section.
6. Click 'Edit' in the 'system startup' section of the new window. This will start a Notepad instance with your boot.ini file displayed. You will need to edit this file in order for your computer to stop looking for the old Windows installation.
7. Click 'File' and select 'Save as'. Save the file as 'boot.old' in order to create a backup of your boot.ini file. You will need this if something goes wrong.
8. Close the Notepad window, and reopen it in the same manner as you did in Step 6.
9. Find the 'bootloader' section in the boot.ini file and remove the line that references your now-deleted Windows installation. If there is confusion as to which is which, refer to the number in the 'partition(x)' portion of the text, where x is a number. The number '1' is equal to the C drive, the number 2 is equal to the next partition's drive letter. So if you have a C drive and a D drive, the C drive would be 'Partition(1)', and the D drive would be 'partition(2).'
10. Save the new boot.ini file and restart your computer. The second copy of Windows has now been successfully uninstalled.