Why do you want to uninstall Ubuntu and then install it again? It seems unnecessary. I would do this:

• sudo apt-get install gparted, then run sudo gparted. Create free space for Windows by resizing your Linux partition(s) as suitable. (This step is unnecessary if Windows is installed on its own, separate physical drive).


• Boot Windows and install into the free space, creating an NTFS partition in the Windows setup. Restart your computer. Only Windows will start, because Windows doesn't care about other OS:es and won't bother to look for them.


• Install EasyBCD in Windows to modify your BCD as suitable, add your Linux installation and set it as default if you wish. This step can be replaced by "repairing" or reinstalling GRUB. It's up to you how you choose to solve it, I prefer EasyBCD as it seems easier to just leave Windows boot menu in place. I usually set a very short timeout (2-3 seconds) as you will get a second menu afterwards with GRUB, that actually does detect Windows, so you can get back to the first menu if you wish anyway. Of course, one could argue that it's cleaner to just fix GRUB. To each his/her own.


• If you choose to use EasyBCD, restart your computer when done and you should get a Windows-like menu asking you what OS to boot, both of them should work.