According to me, your grub is installed on your main drive (drive C:).
Because every time computer booting, it will read the first disk to
looking for MBR= MasterBootRecord(?).
Of, course the grub can be found if moved. But, there no guarantee that
all of the hardware can work, except you use the same component.

To remove ubuntu, you can use Windows CD Installer to repair MBR so
that, windows will loading directly