How can I shrink my Windows partition further than the disk management is allowing?

I had the same problem, 500GB harddisk and the shrinking process didn't shrink less than 230GB.. I did the below steps and I was able to shrink to exactly the space allocated by the windows files itself.

Do the following...

  1. Remove C:\hiberfil.sys file (by disabling Hibernation, e.g with powercfg /h off).
  2. Remove C:\pagefile.sys file (by disabling page file for drive C).
  3. Defragment your C volume.
  4. Restart the computer.
  5. Open disk management and see the magic. ;)

Do not forget to reenable a pagefile after shrinking the volume.

GParted should be able to change the size of the partitions as you want, it can be downloaded from GParted Live CD

BTW, you can have only 4 primary partitions, but if you create one extended partition you can have more logical partitions.

WARNING: Re-sizing partitions can also delete your partition (since you are trying to re-size your root partition, this can happen only if you try to re-size externally (without booting into OS)).

Usually Disk management inside Windows won't allow re-sizing the partition because of unmovable system files. But if you try to defrag your partition, you can shrink it beyond the previously limited size, but of course to some extent. But, third party tools can let you re-size the partitions beyond that too. So, you might want to try one of them. I'd recommend Acronis Disk Director / MiniTool Partition Wizard if you are trying to re-size from inside the Windows, else, GParted Live CD is always the best option.

Make sure that you defrag the drive before trying anything. Also, though GPT scheme allows to create more than 4 primary partitions (128), it also requires that you have to switch from BIOS to UEFI booting. So, if you are going to setup multi-OS system, then you must choose the OSs that support EFI boot.