Disclaimer: Warning, these modifications are done under your own responsibility. HollywoodFX 5.1 is not supported by Pinnacle for Adobe Premiere Pro. This tip and trick should work for all versions of Adobe Premiere Pro. It has been extensively tested with Adobe Premiere Pro CS3.

OVERVIEW:

IMPORTANT: When Windows XP is installed, the default Folder Options setting is to HIDE EXTENSIONS FOR KNOWN FILE TYPES. File extensions are usually three or four letter codes at the end of computer file names that tell the operating system what kind of file they are dealing with. Examples of common file extensions are .EXE,  .JPG,  .BMP,  .AVI, etc

In this tutorial we will be copying some .VFX files from the C:\Program Files\Pinnacle\Hollywood FX 5\Host Plugins folder to the folder C:\Program Files (x86)\Adobe\Adobe Premiere Pro CS3\Plug-ins\en_US folder and renaming them from the .VFX extension to the .PRM extension that Premiere Pro is looking for.

The following step MUST be followed before the file extension can be changed.

From Windows Explorer, select TOOLS/ FOLDER OPTIONS.
From the VIEW tab, UNCHECK "Hide extensions for known file types".  Press OK.
Additionally, it helps to set your display to DETAILS view...

Navigate to C:\Program Files\Pinnacle\Hollywood FX 5\Host Plugins EDITION FOLDER - Contains the "Video Transitions" plugin (HfxEdt5.vfx) - The other file, (HfxEdt46.vfx) can be ignored. EDITIONFILTER FOLDER - Contains the "Video Filters" plug-in (Fl-HfxEdt5.vfx) - The other file (Fl-HfxEdt46.vfx) can be ignored. STUDIO FOLDER - Contains the plugins (.DLL files) for Pinnacle Studio. Disregard this folder for Premiere Pro installation.

You will see three folders: EDITION, EDITIONFILTER, and STUDIO.
Navigate to C:\Program Files\Pinnacle\Hollywood FX 5\Host Plugins\Edition. Right-click the file "HfxEdt5.vfx" and select COPY.
Navigate to C:\Program Files\Adobe\Adobe Premiere Pro CS3\Plug-ins. Hold mouse over en_US folder and right-click PASTE. This will copy the file into the en_US folder. NOTE: If Premiere Pro is not installed with US English as the language, then the name of the folder to paste to will vary. For example, for French the folder is called "fr_FR", etc.
Navigate to C:\Program Files\Pinnacle\Hollywood FX 5\Host Plugins\EditionFilter. Right-click the file "Fl-HfxEdt5.vfx" and select COPY.
Navigate back to C:\Program Files\Adobe\Adobe Premiere Pro CS3\Plug-ins. Hold mouse over en_US folder and right-click PASTE again. This will copy the file into the en_US folder. NOTE: If Premiere Pro is not installed with US English as the language, then the name of the folder to paste to will vary. For example, for French the folder is called "fr_FR", etc.
Navigate to C:\Program Files\Adobe Premiere Pro CS3\Plug-ins\en_US (or installed language folder name - see above) Right-click the file Fl-HfxEdt5.vfx and selct RENAME. Replace the ".vfx" portion of the filename with ".prm" - press ENTER.
Also, right-click the file HfxEdt5.vfx and select RENAME. Replace the ".vfx" portion of the filename with ".prm" - press ENTER.

After renaming the files in the C:\Program Files\Adobe Premiere Pro CS3\Plug-ins\en_US folder from the .VFX extension to the .PRM extension, Hollywood FX Pro 5.1 will be installed into Adobe Premiere Pro as a plug-in. It can be accessed from the Effects Panel, both as a "Video Transition" AND a "Video Effect."

Remember, if your installed language for Adobe Premiere Pro is NOT English, then your plug-ins folder will not contain a "en_US" folder. Adjust accordingly. Hope this helps!

{Thanks to: Bryan Chilcher for this tutorial, Le Papy for uploading it, Loosecannon for the fine tuning}