In this case you have to complete the installation manually. Please follow these steps:
Copy the files with the ending .8bf into the Plugins folder of Photoshop.
For example, Enhancer.8bf from the corresponding folder C:\Program Files\AKVIS\Enhancer\
into the Plugins folder of CS3: C:\Program Files\Adobe\Adobe Photoshop CS3\Plug-Ins\.
Then re-open Photoshop. If the plugins are still not available in the Filter menu, please do the following:
Call the Photoshop command Edit -> Preferences -> Plug-Ins.
Edit -> Preferences -> Plug-Ins...
Select the check-box Additional Plug-ins Folder, then use the button Choose... to select the folder where you've copied the .8bf files.
Actually, you can use any path, any folder which has plugin files. For example, C:\My plug-ins. Or the folder of your image editor (as on the image below - the plugins folder of PSE 5). Or the folder where the plugins installed in Program Files (for example, C:\Program Files\AKVIS\).
Select additional folder
Close Photoshop and open it again for the plugins to load.
Call the plugin from the menu Filter, for example Filter ->AKVIS -> Enhancer.
Select plugins in menu Filter
Attention!
If you still do not see the plugin among Filters please read the documentation for the plugin and check where you can find it.
Some filters show up directly in the main Photoshop menu (typically between "Windows" and "Help" titles).
Some plugins (which change size of images) appear in the menu Automate, for example, the Magnifier plugin:
File -> Automate -> AKVIS Magnifier.
Select automation plugins in menu File -> Automate
For Windows 64 bit
If you set the Additional Plug-ins Folder for Photoshop 32 bit on Windows 64 bit, you can get an error message from Photoshop that it does not know that kind of file.
It happens if the selected folder has a 64 bit plugin. Photoshop 32 bit tries to upload it but can't recognize it.
Not a big problem, but it's very irritating to get the error message each time when you run Photoshop. To remove this error message just delete the 64 bit file from the folder used as the Additional Plug-ins Folder in Photoshop preferences. If you use Photoshop 32 bit you do not need 64 bit files there.
For more information on how to install Photoshop PlugIns on Windows 64 bit please read this article.