By default, apps do not have the permission to write data onto the external SD card in the Samsung Galaxy Tab 7.7. However, there is a hack that lets you accomplish that. It requires you to have a rooted Tab though.
Ready? Here are the steps:
1. Using a root-enabled file manager, navigate to /system/etc/permissions and make sure you have mounted the file system r/w.
2. Edit platform.xml and find the WRITE_EXTERNAL_STORAGE permission.
3. Add an additional group definition for this permission.<group gid=”media_rw” />
4. Save the changes to the file.
5. Restart your Galaxy Tab.