I have used Easeus for all my partition management under Windows. When you ask it to perform a function that needs total control of the disk, it will re-boot the PC and run the desired function before letting the PC boot Windows. It has yet to fail me.
Like all major changes to your PC, have a solid backup before making changes.
The re-boot is like when you ask Windows to do a scan on your ‘C’ disk where Windows is booted from. Windows will inform you it can not do the scan until the PC is re-boot. Windows utility runs the scan after the re-boot and before Windows is loaded.