So are you saying you can't copy pictures, document files, etc..? Either this be with a removable drive or discs, you can copy it's contents and put it somewhere else; just like backing up your data somewhat. If it's partitioned, you might have to set permissions to allow it to copy over.
Right click on the "My Documents" folder, select properties, and change the target to the new hard drive. Then all the current files will be moved there, and Windows will associate the new hard drive as the permenant place to store the My Documents folder.