As Adobe Illustrator 4.x does not support loadable palettes, except as a part of the document. Illustrator native files will be copied to your hard disk by the installation program. If you used the suggested location, they will be in the C:\HPANTONE\ILLUSTR directory.
The following procedure assumes that the file is opened in Illustrator.
To select and load an HP PANTONE (R) Palette File
Choose File, Open.
Use the file system navigator to go to the C:\HPANTONE\ILLUSTR directory.
You will see two entries; double-click the appropriate HP PANTONE (R)* palette in the list.
From Paint, select Custom Color. The list now contains the HP PANTONE (R)* colors from the palette file selected (these are available for use in your drawing).