Fought with the Windows Disk Manager for way too long this morning trying to shrink a partition with plenty of space so that I could setup a native dual boot...

Screw that tool, I resized the partition to nothing by formatting it.

Try using minitool partition wizard

Ehhhh.... Did you defrag before?

I've always had good luck with EaseUS Partition Master.

@apex It's an SSD, I did trim it though.

I took these steps:
- Installed all updates and then ran Disk Clean to clear out temp files, logs and update caches
- Disabled system restore and deleted all restore points
- Disabled page file on all drives
- Disabled hibernate
- Deleted all unused applications and cleared browser caches.

It is a 180GB SSD, 155GB dedicated to Windows 10.
I cleared enough space to have 92GB free without affecting my development environment or installed applications.
I tried to carve out 48GB of the 92GB free and Disk Manager even reported I could carve out 75GB.

Nothing worked... It kept saying there wasn't enough space even when I dropped to a smaller 25GB shrink.

Well that's odd, but as they've said here before, try Minitool, it works like a charm