Windows enforces strict data security boundaries. Software requiring direct block-level access to a drive—such as TransMac writing an Apple HFS+ or APFS filesystem—must request an exclusive lock from the operating system.
Before applying the fix, it helps to understand the cause. Windows treats external drives differently than macOS does. The error typically occurs for one of three reasons:
Some USB drives and SD cards have a physical lock switch on the side. If your drive includes this feature, make sure the switch is not in the locked position. transmac drive has been locked by another program hot
Toggle to Off temporarily while using TransMac.
: Actively checking the newly inserted drive for malware. Windows enforces strict data security boundaries
Right-click the process locking it (often explorer.exe or security tools) and select . The Ultimate Fix: Wipe and Reset with Diskpart
Ensure no other third-party disk management or file system tools are accessing the drive. If any are, close them. Windows treats external drives differently than macOS does
The error is rarely a sign of a failing drive. It’s almost always a Windows resource conflict . By systematically unmounting the drive via DiskPart, killing handle-holding processes, or disabling Fast Startup, you can successfully bypass the lock and write to your Mac drive without data loss.
. This removes all partition info and usually breaks any existing software locks. Check TransMac Settings
If your drive was previously used with TransMac but is now corrupted or locked, reformatting it might be necessary.