You may recieve an error message when you try to open a file saved in Word
format.The error message appears like :"You are attempting to open a file
type that is blocked by your registry policy settings".To resolve this problem
insert or modify the following registry key:

- HKEY_CURRENT_USER\Software\Policies\Microsoft
\Office\12.0\Word\Security\FileOpenBlock\

Create here in the right pane one or more REG_DWORD [DWord Values]
according to the table below :

BinaryFiles : .doc , .dot
RtfFiles : .rtf, .doc (Word 95), .doc (Word 97 original release version)
Converters : All file formats that are available by using a text converter
InternalFiles : All Word file types that have a non-RTM nFib value
FilesBeforeVersion : 101(value) corresponds to Word 6.0 for Windows
and allows all older file types. (that is what is needed in most cases)

Note:except FilesBeforeVersion value 1 blocks and value 0 allows the
specified file types.

There is the same option for file types which cannot be saved.Create under
the Security subkey a key called :

File SaveBlock (Create here in the right pane entries according to the table
above.)(no InternalFiles and FilesBeforeVersion here !!!)