To install a downloaded fixture library for MSD, first unzip it, which will create a folder called 'spots', and sometimes a folder called 'gobo'.

Move (or copy) everything from the 'spots' folder to the MSD spots folder, which is :
'C:\Program Files\MSD4\Spots'
or
'C:\Documents and Settings\All Users\Documents\MSD4\Spots' (Windows2000 or higher, MSD 4.3 or higher)
when you have MSD installed in the default location.

In the same way, move (or copy) everything from the 'gobo' folder to the MSD gobo folder, which is :
'C:\Program Files\MSD4\Gobo'
or
'C:\Documents and Settings\All Users\Documents\MSD4\Gobo'

For the Martin LightJockey Visualizer, these folders are located in a subfolder of where the Martin LightJockey is installed.

After this, you can remove the folders which were created by unzipping the downloaded file (and the downloaded zip file if you want).