"0x80070057" error message when you back up files in Windows 7

To resolve this problem, use one of the following methods:
 

Method 1: Change the decimal symbol setting

This problem can occur if the decimal symbol is not set to '.' (dot). This is common in languages and locales other than English (United States), such as German (Germany).

To change the decimal symbol setting, follow these steps:

1. Open Control Panel, click Clock, Language, and Region, and then click Region and Language.
2. Click the Formats tab, and then click Additional settings.
3. In the Decimal symbol field, type . (dot), and then click OK two times.
4. Restart the computer.

Note Some third-party software may cause changes to the runtime locale of the computer and override the setting in Control Panel.

Method 2: Add a registry key value

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
 

1. Click Start , type Regedit.exe in the Search programs and files box, and then press ENTER.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\System
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type CopyFileBufferedSynchronousIo, and then press ENTER.
5. Right-click CopyFileBufferedSynchronousIo, and then click Modify.
6. In the Value data box, type 1, and then click OK.
7. Exit Registry Editor.