Troubleshooting Disk Partitioning Issues on C: Drive
Introduction
Disk partitioning is a common administrative task, whether for organizing data, improving system management, or preparing servers for specific workloads. However, while attempting to shrink the C: drive in Windows to create a new partition, administrators may encounter a frustrating error:
“You do have free space, but Windows cannot shrink it because of unmovable system files near the end of the C: drive.”
This error occurs even when the drive clearly shows sufficient free space. The root cause is typically the presence of system files that Windows cannot move automatically. This article explains why this happens and provides a step-by-step approach to safely resolve the issue.
Understanding the Problem
Windows Disk Management can only shrink a volume up to the point where the last unmovable file is located. These files often include:
Page file (pagefile.sys)
Hibernation file (hiberfil.sys)
System restore data
NTFS metadata
CryptoAPI RSA key containers
When such files exist near the end of the disk, Windows prevents further shrinking, even if large amounts of free space are available elsewhere.
Step 1: Verify Settings and Prepare the System
Before making any changes:
Ensure you are logged in with administrator privileges.
Confirm that sufficient free space exists on the C: drive.
Take a backup or snapshot (especially on production servers).
Schedule downtime if the system is critical, as restarts are required.
Preparation reduces the risk of data loss and ensures changes can be safely applied.
Step 2: Disable the Page File Temporarily
The page file is one of the most common unmovable files preventing disk shrinking.
Steps:
Right-click This PC → Properties
Click Advanced system settings
Under Performance, click Settings
Go to Advanced → Virtual Memory → Change
Uncheck Automatically manage paging file size for all drives
Select C: → choose No paging file → click Set
Restart the system
Disabling the page file allows Windows to relocate disk data more effectively.
Step 3: Defragment the Drive
Defragmentation consolidates free space and moves files toward the beginning of the disk.
Command:
Open Command Prompt (Run as Administrator) and execute:
What this does:
Moves files to consolidate free space
Attempts to free contiguous space at the end of the volume
Increases the maximum shrinkable size
Note: This step is most effective on HDDs. On SSDs, Windows performs optimization differently, but the command is still safe.
Step 4: Check Event Viewer for Errors
If shrinking the volume still fails:
Open Event Viewer
Navigate to Windows Logs → System
Look for warnings or errors related to:
Disk
NTFS
Volsnap
Partition or storage drivers
These logs can reveal underlying issues such as file system corruption or driver-related problems that block disk operations.
Step 5: Remove Problematic CryptoAPI RSA Key Containers
In some cases, unmovable system files are caused by CryptoAPI RSA key containers stored under the LocalService profile.
Location:
Action:
Navigate to the directory
Remove the files inside the RSA folder
⚠ Important Warning:
These files store encryption keys used by Windows services
Removing them may reset certain cryptographic keys
Always back up the directory before deletion, especially on domain controllers or certificate authorities
This step has proven effective in cases where Disk Management reports unmovable files despite other optimizations.
Step 6: Restart the Server
After completing all changes:
Restart the system to release file locks
Allow Windows to rebuild required system files
Once the server is back online, retry shrinking the C: drive using Disk Management.
Final Summary
The “unmovable system files” error during disk shrinking is a common Windows limitation rather than a lack of free space. By following a structured approach:
Temporarily disabling the page file
Defragmenting the disk
Reviewing system logs
Removing problematic CryptoAPI key containers
Restarting the system
administrators can successfully shrink the C: drive and create new partitions without reinstalling the OS or using third-party tools.
This method is especially useful for system administrators, IT engineers, and security teams managing Windows servers and workstations.
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