Force showing of known file extensions

In the registry go to :
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Currentversion\explorer\Advanced\Folder
and then there is a sub key Hidden with 3 subkeys, NOHIDDEN, NOHIDORSYS,
SHOWALL. The default value for all these 3 is (0), and the checked values are
(2), (0), (1) respectively.

The next subkey of Folder is HideFileExt, and the checked, unchecked, and
default values are (1), (0), (1) respectively.

These values tell you what to change in this key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\Currentversion\Explorer\Advanced\
In the right hand pane are listed the features such as Hidden, and
HideFileExt , and the data values that be be switched from 0 to 1 etc.

If you manually change the values, eg HideFileExt, the file extensions
change immediately from showing to hidden and vice versa.

One thing I cant see is a separate value for hiding system files.

Without actually doing all the work, the reg file way would be to export
this key to a reg file, then make another with the switches changed.
Then copy the *.reg file to the netlogon share and add a batch command in
the netlogon bat file. Something like:

regedit /s <path to *.reg file>

Found this info at: http://www.itnewsgroups.net/windowsserver/t1372-hide-file-extension-using-group-policy.aspx