If Windows reports “the semaphore timeout period has expired,” stop the failed transfer and find out where the delay occurred. A removable drive that disappears, a network share that drops, and one unreadable file require different responses. Keep the original files untouched while you test a small copy. If an external drive clicks, disconnects repeatedly, or freezes the computer, stop scanning it. Protecting the data is more urgent than making the message disappear.
What timed out: the file, the device, or the route?
Windows identifies this message as error 121, also called ERROR_SEM_TIMEOUT in its system error list. The code says the operation waited too long. It does not identify a failed disk by itself. Write down the exact action, source, destination, and whether the drive stayed visible. Those four observations are more useful than repeatedly pressing Retry.
Imagine copying photos from an external drive to your PC. If the drive disappears from File Explorer as the message appears, inspect the USB connection and power. If the drive stays visible but the same photo always stops the copy, the file or its area of storage may be unreadable. Copies from the external drive to the PC may work while copies to a shared network folder fail, test the network destination. This simple comparison keeps you from repairing the wrong device.
Use one small, unimportant file for each test. A whole-drive copy reads many areas and can mask the first point of failure. If your files are irreplaceable, note which folders still open and which do not. Do not move originals during diagnosis; copying leaves the source in place. If a copy succeeds, open it at the destination before assuming the transfer was complete.
Make one safe connection check
For a USB drive, close the file window and shut down any app that is actively reading the device. Disconnect it using Windows Eject when possible. Reconnect it directly to another known-good USB port, without a hub. If the drive has its own power supply, confirm that it is connected correctly. For a portable hard drive, a short known-good cable can rule out a loose connection. Avoid repeated unplugging when the drive is making unusual sounds or its power state is unstable.
Open File Explorer and check whether the device appears with its usual capacity. If it does, try a small copy from a different folder. Do not accept a Windows prompt to initialize or format it. A format prompt means Windows cannot read the existing file system; formatting would create a new one. If the device appears only intermittently, stop here. A stable image made by a specialist may preserve more than another series of direct copy attempts.
If several unrelated devices fail on the same port, the computer or port deserves attention. If only one device fails across multiple computers and cables, its enclosure or media may be at fault. A USB adapter can fail while the disk behind it is still readable. Opening an enclosure, however, can be risky and may affect warranty or hardware encryption. Seek qualified help when the files matter and you are unsure how the device is built.
When the copy stops at the same file
A repeatable stop at one file is different from random disconnects. First see whether the file opens without editing. For a photo, inspect the full-size image rather than a thumbnail. For a video, play more than the opening seconds. If it opens, copy it alone to a healthy local drive and verify the result. If it fails but nearby files copy, note the affected name and keep copying other accessible files in small groups. Do not make that one file the reason to scan the entire source repeatedly.
Try a different reader or computer only if the device is stable and the test will not require formatting. A recurring timeout at one location may indicate damaged file contents or a difficult area of the medium. It can also be caused by the application handling that format. Compare whether the same file opens in another viewer, but work from a copy whenever possible. If the source is an SD card, do not put it back into a camera that may write new media over deleted files.
A copy that fails at changing files while the drive remains connected suggests a broader access problem. Check whether free space is available on the destination. Look for a security app or backup job working on the same folder. If Windows begins reporting I/O errors or File Explorer freezes when you open the drive, move to data protection rather than running a repair command. The separate I/O device error guide explains that wider symptom.
Protect files on a stable, readable device
Check backups before scanning. A cloud copy, File History version, or earlier external backup can restore a needed file without more reads from the troubled source. If the device is stable and files have gone missing, avoid writing new data to it. Do not install recovery software onto the same partition. Prepare another healthy drive with enough space for the files you may retrieve.
Drecov is Windows data recovery software for a stable, detectable PC disk, external drive, USB drive, or memory card. In this situation its role is to locate files that are missing or inaccessible after a failed transfer, not to repair the cable or eliminate a timeout. Its read-only recovery mode, Quick Scan, Deep Scan, file filtering, and preview let you examine candidates before saving them elsewhere. Lost Partition Recovery is available if a previously present partition is missing, but file recovery does not rebuild a partition table. If the device drops offline, clicks, or reports severe read errors, stop direct software scans and consider an image or professional recovery.
⚠ Warning: Install it on a drive different from the one where your data was lost to prevent overwriting.
Step 1: Open Drecov and choose where the files were lost
Connect the separate healthy destination first. Open Drecov from the computer’s healthy system drive and select the original disk, partition, or removable device. Use the capacity and device label to confirm it. If the former partition is absent but the physical device is stable and correctly detected, choose the relevant Lost Partition Recovery mode. Do not initialize the disk to make it appear in Windows.
Step 2: Start Quick Scan
Run Quick Scan on the original location. Check the folder that held the interrupted photos, documents, or videos. Look for the expected file names and compare dates. A file listed in a scan is only a candidate; it may still be incomplete if the source was failing during the original copy.
Step 3: Use Deep Scan only if the device remains steady
If the needed items are absent from Quick Scan, continue with Deep Scan only while the device stays connected and responds normally. Stop if the same hardware errors recur or scan progress repeatedly stalls. A professional can sometimes work from a controlled image instead of stressing the original medium.
Step 4: Filter and preview useful results
Filter by former path, type, size, or date. Preview several representative files, including one from the folder that failed to copy. For large videos and archives, a preview cannot prove that every frame or archive member is intact. Recover a small sample and test it in its normal application before selecting thousands of files.
Step 5: Save and verify away from the source
Recover selected files to the healthy destination, never to the timed-out source. If the output is not in the expected folder, check the Drecov Folder or Recovery Folder there. Open important documents, play several parts of videos, and compare file counts with your backup or original folder listing. Only after those copies pass should you consider file-system repairs or reformatting a reusable device.
⚠ Warning: Install it on a drive different from the one where your data was lost to prevent overwriting.
A timeout while copying to a shared folder does not prove that the source drive is damaged. First copy the same small file to a local healthy folder. If the local copy works, check the network route and share. Make sure the target computer is awake, the share opens normally, and the network connection is stable. Try a second small file in the same destination. A failure limited to the share belongs to its connection, permissions, or server rather than to data recovery on the local source.
If a large transfer fails over Wi-Fi, a temporary wired connection may help you test stability. Ask the share administrator whether other users see the same timeout. Keep the local verified copy until the remote transfer completes. If the only existing copy is on the shared drive and that drive itself is unstable, do not assume Drecov can scan it over a network path. The storage owner may need local access to the physical disk or a server-side backup.
After protecting the data, decide whether the device itself deserves repair. If a drive fails across direct ports and another computer, the external-drive diagnosis helps separate enclosure, file-system, and media faults. If the device is healthy but only the copy operation fails, follow the broader copying checks. Do not use CHKDSK, formatting, or partition changes until the important files are independently verified.
Conclusion
“The semaphore timeout period has expired” means an operation waited too long; it does not name the faulty part. Test one small file and compare local, USB, and network paths. Stop if a drive becomes unstable. For a stable device with missing files, Drecov can search the original location, preview useful results, and save recoverable copies to a healthy destination. Verify those files before any repair that writes to the source.
⚠ Warning: Install it on a drive different from the one where your data was lost to prevent overwriting.
