Help I can't shrink my C: drives partition

Windows has limited partitioning ability, when it meets an unmovable file, it will refuse to shrink the partition any further, usually it is the MFT (disk index) file that stops Windows shrinking the drive any further, you will need to use a 3rd party tool like the free version of AOMEI Partition Assistant to shrink the partition, and before doing that, to avoid data loss, backup all your files in case the process fails.

If you're unable to shrink your C: drive partition in Windows, there are several factors that could be causing the issue. Here are some detailed steps and considerations to help you troubleshoot and resolve the problem:

1. Check for Unmovable Files: Certain files on your C: drive, such as the paging file, shadow copies, or system files, cannot be moved. This can prevent the shrink operation from succeeding. To identify unmovable files, check the application log for an event with ID 259, which will provide information about the file blocking the operation.
2. Use the fsutil Command: You can use the fsutil command to identify the specific unmovable file. Open a command prompt and run the following command:

      fsutil volume querycluster C:
   

   This command will display information about the unmovable file that is preventing the shrink operation. For more details on using this command, you can enter fsutil volume querycluster /? in the command prompt.
3. Temporarily Relocate Files: If you find that the paging file or shadow copies are blocking the shrink operation, consider temporarily relocating them. You can do this by:
   • Moving the paging file to another disk via Control Panel.
   • Deleting stored shadow copies if they are not needed. After relocating or deleting these files, try shrinking the volume again.
4. Bad Clusters: If your disk has a high number of bad clusters, this can also prevent shrinking. You can check for bad sectors using the built-in Windows tools. If bad clusters are detected, consider backing up your data and replacing the disk. Avoid using block-level copy operations to transfer data, as this can copy the bad sector table.
5. Disk Management Utility: Use the Disk Management utility to visualize your partitions and their status. You can access it by right-clicking on the Start button and selecting "Disk Management." This tool will show you the layout of your drives and any existing partitions, helping you identify if there are any issues with the partition structure.
6. Free Up Space: Ensure that there is enough free space on the C: drive before attempting to shrink it. If the drive is nearly full, it may limit the amount of space you can shrink.
7. Consider Third-Party Tools: If Windows Disk Management continues to fail, you might consider using third-party partition management software, which can sometimes handle more complex partitioning tasks more effectively than the built-in tools.

By following these steps, you should be able to identify the cause of the issue and successfully shrink your C: drive partition to create space for a new partition.

References:

• Shrink a basic volume
• Other considerations
• Overview of Disk Management