I don’t know of any Ubuntu tool that will fix Windows broken boot files, if that us the problem.
If windows is working, linux (grub on ubuntu) can detect the windows install, and add the working boot option to grub’s list of bootabke OS’s. So dual boot, with Windows already install, can Add windows to the grun options.
If the boot files in windows are wonkey, and you are not dual booting, then I would say, try to fix them with a windows install drive or similar?
I am presuming you only have 1 drive in the machine, and wish to have windows as the only OS.
If the windows install, simply needs registering with the motherboard, then installing linux to another drive/partition, which installs grub, might additionally register the windows install with the motherboard as well, but would be a longer way around.
You could use a Ubuntu USB drive, and try to run the “fix-mbr” tool, but I am not sure it works on a liveUSB system; never tried…
Perhaps might work? But never tried