The Hydraulic.zip file contains contains 4 drawings which contain hydraulic and pneumatic symbols that were available in Symbols 97/98, but were inadvertantly left out of Symbols 2000. 

Save the file to your local hard drive.

Double-click on the file to extract the four drawings.  Extract them to the desired directory.  By default, symbols are located in the following folder:
<drive>:\Program Files\Autodesk Symbols 2000\.