1. Check the physical switch: Some USB flash drives are equipped with physical switches for setting the write-protect status. Before solving the problem, check whether there is such a switch on the shell of the USB flash drive and make sure it is in a writable state.

2. Modify the registry: By modifying specific key values ​​in the registry, you can turn off the write protection of the U disk. Specific steps include opening the Run window, typing regedit and pressing Enter to open the Registry Editor, then navigating to the specific path and modifying or creating the corresponding DWORD value.

3. Change the disk policy: Remove the U disk write protection by changing the disk policy. The specific steps include opening My Computer, finding the U disk and selecting the Properties window in the U disk drive letter, then clicking Hardware, Properties, Policy, and changing it to "Better Performance" in the Policy item.

4. Run anti-virus software: If the U disk cannot be modified, it may also be because the computer itself is infected with a virus. You can first use anti-virus software to try to eliminate the virus. Generally, after the virus disappears, the USB flash drive can return to normal.

5. Format the USB flash drive: If none of the above methods work, the last resort is to try formatting the USB flash drive. But please note that this will delete all data on the USB flash drive, so make sure to back it up in advance.

Before trying the above methods, be sure to back up important data in the USB flash drive to avoid unnecessary losses. If the problem still cannot be solved, it is recommended to consult professional technicians or relevant manufacturers for more specific help and support.