Gparted seems to recommend to hell with diskmgmt.msc shrink, but rather, just go ahead with the re-partition chopping off all the (mid disk) system files (paging files, hibernation file and system restore files as mentioned above) and then use the pre-created system recovery disk to restore sense to your C drive if Windows does not boot.
Turning off paging then defragging took hours with no reduction in post-shrink size and likewise turning off hibernation did nothing for me at all. Plus I have already cloned my hard disk to another hard disk of the same (1TB) size. My problem is allowing me to use a 500GB SSD.
So I created a System Recovery Drive on an 8GB USB, Gparted my main drive to half or 480GB, inserted my recovery drive (that took a couple of hours to make) and my recovery drive was ignored in the boot!
But, Windows on the halved disk booted fine. I just ran a disk check and repair (and there seemed to be mention of "10 of 10" repairs? maybe) and windows has booted fine. I have turned my paging file back on. I still have my 1TB HDD clone, so I will now go ahead with Clonzilla clone to my 500GB SDD.
I did that but alas clone partition does not move the MRB.