A completed copy window is one checkpoint, not the whole end of a storage task. Microsoft documents the Safely Remove Hardware and Eject Media workflow in Windows. Use the removal procedure appropriate to the device rather than pulling a cable because the screen looks quiet.
Finish the task you actually started
Imagine copying a folder, then opening one of its documents directly from the external drive. The copy is finished, but your work with the drive is not. Save any edits, close the document and wait for other known transfers or backup tasks to finish.
Use the Windows eject control and select the intended device. Check its name carefully when several drives are attached. Wait for the system's confirmation before disconnecting it.
If Windows says it is still in use
- Look for documents or media opened from that drive.
- Check known copy and backup applications.
- Close the relevant work normally rather than force-quitting at random.
- Retry removal after those tasks finish.
Do not delete files or change caching policies just to dismiss the message. If the device remains busy and the cause is unclear, follow the documentation for your exact setup. A working backup matters more than saving a few seconds at the cable. Safe removal is a routine step, not a guarantee against every possible device failure.