Reinstalling
After a couple days of trying to transfer my DAZ library to my secondary D: drive, due to my C: drive getting too full, I ended up deciding to go the nuclear method and uninstalled DAZ and deleted all DAZ system files from my computer, and reinstalling from scratch.
I reinstalled DAZ and specified in the Installation Settings that the "My DAZ 3D Library" folder should be directed to my D: drive, but when I try to install any packages, they won't install and I just get a "Retry" error button (DAZ Studio and Postgre SQL both installed fine):
This is the error message that's appearing in the log:
2025-03-20 15:13:18.339 [WARNING] :: Extract File Failed - : D:/Program Files/DAZ 3D/My DAZ 3D Library/data/Daz 3D/Genesis 9/Base/Tools/Script Loads/SnowQueen 9 Makeup/MakeupRoughnessUtility.dse
2025-03-20 15:13:18.418 [WARNING] :: Install Failed: Snow Queen LIE Makeup Collection for Genesis 9
2025-03-20 15:13:18.514 [INFO] :: Install Queue Finished: 0 min 0.2 sec
I've tried switching the My Daz 3D Library directory back to my C: drive, just to see if that would get the packages to install, but that just yielded the same error seen above.
I've tried the nuclear approach a few times now, and I'm still not making any headway. Any advice would be greatly appreciated.

Comments
The operating system generally protects the Program Files folder - it is not a good diea to put your content in that, even if it is on a different drive.
Adding to what Richard said, you'll want to try mirroring the original installed data folder tree as much as possible, which means creating the [new drive letter]:/user/Public/Public Documents/DAZ 3D/..... And be sure to redirect your DIM installation listings, too. As for the DAZ Studio and other 3D applications, those are okay to put into the /Program Files/ & /Program Files(x86)/ folders in the new drive.
However, there are likely some items, such as cms and JSON folder/files which will insist on being in the C:/ drive, but those are a minimal impact on your disk space.
edited-->TBH, having been a computer tech in the Government, I've never been comfortable to putting anything into the Public account folders, as that potentially opens up a ton of security holes in your system. However, you can keep your system safe by ensuring any logon into the Public user is disabled. You need only to allow your authorized users access to those Public data files.
Good luck! I've had lots of fun doing that several times over the course of a few decades.
The better way is to always set the directories of your Daz Libraries in another disk ~~