Fix STATUS_PARTIAL_COPY (0x8000000D) File Copy Error

You're copying a folder full of documents—maybe from an old laptop backup or a network share—and halfway through, Windows stops with STATUS_PARTIAL_COPY (0x8000000D). The error says "not all the requested bytes could be copied." But here's the weird part: some files made it. Others didn't. And the ones that failed copy fine if you try them individually later. This tripped me up the first time I saw it on a Windows 10 Pro machine migrating data off an encrypted drive.

What Causes STATUS_PARTIAL_COPY?

The root cause is almost always Encrypting File System (EFS)—that's the transparent encryption built into NTFS, not BitLocker. When you try to copy or move an EFS-encrypted file across drives or to a network location, Windows checks the encryption certificate. If the destination doesn't support EFS decryption on the fly, the copy fails with partial data. But there's a second trigger I've seen: NTFS permission conflicts where the source file has explicit deny entries or inherited permissions from a protected folder (like a user profile's AppData). The system starts copying, hits a protected block, and aborts.

How to Fix It (Step by Step)

Decrypt the source files first
Open an elevated Command Prompt (right-click Command Prompt, Run as administrator). Navigate to the folder with the partial copy error. Run:
```
cipher /d /s:"C:\Path\To\Your\Folder"
```
This decrypts all files and subfolders in that directory. You'll need the original EFS certificate—if you've never backed it up, this is where things get sticky. For most users on a single machine, it works because the cert is stored in your user profile.
Check and reset permissions
If decryption didn't help, permissions are the culprit. Right-click the source folder > Properties > Security > Advanced. Look for any Deny entries. Remove them. Also, make sure the destination folder gives your account Full Control. Do the same for the destination.
Use robocopy with retry flags
Don't rely on Windows Explorer for this. Open a new Command Prompt and run:
```
robocopy "C:\SourceFolder" "D:\DestFolder" /E /R:3 /W:5 /COPY:DAT /ZB
```
The /ZB flag uses backup mode, which can bypass some permission blocks. The /E copies subdirectories including empty ones. /R:3 retries three times on failure. This command saved me on a 50GB migration where Explorer kept dying at the same file.
Turn off EFS temporarily
For a bulk copy, you can disable EFS decryption on the destination by modifying a registry key. This is advanced, so back up your registry first. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem, create a DWORD called NtfsDisableEncryption, set it to 1. Reboot. After the copy, set it back to 0 or delete the key.
Check disk health
Rare, but bad sectors can cause partial reads that trigger this error. Run chkdsk /f on both source and destination drives. I've seen this on a failing external USB drive where the first few bytes of a file were readable but the middle wasn't.

Still Failing? Check These

Antivirus real-time scanning—temporarily disable it. Some AVs lock files mid-copy.
Network share permissions—if copying over the network, make sure the share and NTFS permissions don't conflict. A common mistake: share allows Everyone Read, but NTFS has Deny for your user.
File names too long—Windows has a 260-character path limit. Use robocopy with /256 to handle long paths, or enable long paths in Group Policy.

STATUS_PARTIAL_COPY is one of those errors that looks scary but has a clear fix path. Start with decryption—that's the trigger 8 times out of 10. If you're still stuck, the robocopy approach with backup mode usually bulldozes through the rest. Let me know if it doesn't—there's always a workaround.