Fix error 0X00000964: device is being accessed by active process

1. Your antivirus or file sync app is locking the device (most common cause)

This error shows up a lot when you try to open a USB drive, external hard drive, or a network share. The real trigger is often something like OneDrive, Google Drive, or your antivirus program doing a background scan on the device.

When you see the error 0X00000964 with the message "the device is being accessed by an active process," the simple fix is to pause or close these apps first.

Step-by-step fix:

1. Close any open file explorer windows that show the device. Press Ctrl + Shift + Esc to open Task Manager.
2. Look under Processes tab for OneDrive, Google Drive, Dropbox, or your antivirus program. Right-click each one and select End task.
3. After you end those tasks, wait 10 seconds. Then try accessing your device again. It should work now.
4. If it does work, permanently exclude your external drives from real-time scanning in your antivirus settings. For OneDrive, go to OneDrive Settings > Account > Choose folders, and uncheck the device you're having trouble with.

Expected result after step 3: You should see the device's contents in File Explorer without any error.

2. A program has a file open on the device (second most common)

This happens when you leave a program running that's opened a file on the device. For example, you might have a video player playing a movie from your external drive, or a text editor editing a file there. When you try to safely remove the drive or access it from another PC on the network, you get the 0X00000964 error.

Step-by-step fix:

1. Save all your work on files that are on that device. Then close every program that might have opened a file from the device. This includes Word, Excel, video players, photo editors, and PDF readers.
2. If closing programs doesn't work, open Task Manager (Ctrl + Shift + Esc). Go to the Performance tab. Check disk activity. If the device shows high activity, a background process is using it.
3. The real fix for stubborn cases: download Process Explorer from Microsoft (it's free). Run it as administrator. Press Ctrl + F to open the search box. Type the device letter (like E:) and press Enter. Process Explorer will show you exactly which process is holding a file on that drive.
4. Right-click the process in the results and select Kill Process. Then try accessing your device again.

Expected result after step 4: The error should be gone. You'll see your files normally.

3. Windows is still caching the device (network drive or USB issue)

This one's common on network drives and external drives that were disconnected improperly. Windows holds onto the device in a "ghost" state. The error shows up when you try to reconnect or access it.

Step-by-step fix:

1. Open Command Prompt as administrator. Search for "cmd" in the Start menu, right-click it, and choose Run as administrator.
2. Type this command and press Enter:
   

   net use * /delete

   This will disconnect all mapped network drives and clear the cache.
3. If the device is a USB drive, unplug it physically, wait 30 seconds, then plug it back in.
4. For USB devices, also run this in the same Command Prompt window:
   

   diskpart
   list volume
   

   Find your device in the list. Type select volume X (replace X with the volume number). Then type offline volume, wait 5 seconds, then type online volume. Type exit to leave diskpart.

Expected result after step 4: The device should show up without any error. You might need to assign it a drive letter in Disk Management if it doesn't appear.

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