Based on @alacran's post (and also mentioned by @antonino61), I used DiskGenius portable to get the job done. (The original question was which tool to use to extend the Windows system (C:) drive). He mentioned that tool, as well as MiniTool. I have used Minitool in the past, and liked it, but its most recent versions have require the paid version for many functions, including resizing the system partition. His post also mentioned DiskGenius being able to create its own WinPE bootable USB drive, which feature I used, and it worked well.
In addition, DiskGenius allowed the C: drive to be extended with the free space that was on the other side of the Recovery partition, and it automatically moved the Recovery partition to the end of the free space. That was very convenient!
I found the DiskGenius UI, and its operation, to be less intuitive and harder to use than some of the other tools. But functionally, with all the capabilities offered (even in the free version), I rate it tops, and wouldn't hesitate to use it again.
Immediately before running the DiskGenius WinPE (which I had previously created), I used Clonezilla to back up the system and recovery partitions. Immediately after running DiskGenius, and booting into Windows without any issue, I ran Disk Management, and it showed everything as it should be, with the recovery partition apparently intact.
@karyonix, thanks for your posts with instructions on handling the Recovery partition. DiskGenius apparently took care of that automatically, but if it hadn't, or if any issues should arise involving the recovery partition, your instructions will be very helpful.
Thanks to all who offered suggestions. I've marked this thread as answered, since the original question has been addressed. But I still intend to follow up and try to get some of the mentioned tools working under GRUB4DOS.
@AnonVendetta suggested using Easy2Boot to run the tools, and then examine the parameters used there, which I did. It was a good suggestion, but unfortunately using the discovered parameters didn't result in success. I've still had no success with GParted under G4D, although that's less of an issue now, since GParted can be run with Puppy Linux under G4D. But it would still be nice to solve.
SystemRescueCD has been a little bit better, and I feel that a solution may be close. Based on this SystemRescueCD website page: https://www.system-r...ue_on_the_disk/ I have the .iso booting under G4D to a more advanced stage, but it is now showing:
:: Mounting 'dev/disk/by-label' to '/run/archiso/bootmnt'
Waiting 30 seconds for device /dev/disk/by-label/ ...
On the page mentioned, it says that archisolabel must be set to the label of the NTFS filesystem which contains systemrescuecd. I've tried setting it to the label of the E: (FAT32) drive where the systemresuecd .iso is located, which resulted in the above error. I've also tried setting it to 'RESCUE803' which is what is used in the configuration file in the .iso itself, but with no change. I really don't know what it wants to have that parameter set to.
So that's the status to this point. Any further comments welcome.