Registry Method
- Make sure that your files and folder have been synchronized. Reinitializing the cache prior to synchronizing will cause you to lose any data that isn’t synchronized.
- Click Start, type regedit in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for a confirmation, type the password, or click Continue. - Locate the following registry subkey, and then right-click it:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CSC
- Point to New, and then click Key.
- Type Parameters in the box.
- Right-click Parameters, point to New, and then click DWORD (32-bit)Value.
- Type FormatDatabase, and then press ENTER.
- Right-click FormatDatabase, and then click Modify.
- In the Value data box, type 1, and then click OK.
- Exit Registry Editor, and then restart the computer.
Source: http://www.mgdking.com/post/How-To-Reinitialize-The-Offline-Cache-in-Windows-7