The Photoshop plugin for Pixel Bender filters was not included in the Photoshop installer for cs5. The "Pixel Bender" that shows up in your installation is the Pixel Bender Toolkit, which is the development environment for creating and editing Pixel Bender filters. You can download and install the Pixel Bender plugin for free, as a Photoshop Extension from Adobe Labs (http://labs.adobe.com/technologies/pixelbenderplugin/).
Thank you for your interest in and enthusiasm for Pixel Bender. Pixel Bender has been offered in the past on Adobe Labs as a technology preview (http://labs.adobe.com/about/). It was never a shipping/officially supported product/feature: http://labs.adobe.com/about/faq/#itemA-8. As of CS6, we are no longer providing Pixel Bender as a Labs technology. Photoshop CS6 has taken the Pixel Bender filter most popular with customers, Oil Paint, and turned it into an official feature in CS6. Photoshop CS6 no longer supports Pixel Bender for 3rd party development.
I encountered the same problem and just spent almost 3hours looking for a solution and I found one!! A well explained video on utube! and it works, I run CS5 on windows 8 but the rules are the same. I really hope it helps you.
here the link and title of the video
How to download & install Pixel Bender
The links he shows to download the program have changed, so in case you don't have the download anymore go to
Pixel Bender Toolkit 2.5 for Windows (ZIP, 59 MB) it is on the left under the icon
Proceed with the installation then be ready for the magic step 2
Now from the same page that you just downloaded the Pixel Bender toolkit scroll down to the "Archived downloads"
and download Pixel Bender plug-in for Photoshop CS5 (12.1) (Win 32–bit) or Pixel Bender plug-in for Photoshop CS5 (12.0) (Win 32–bit) With all my tries I can't remember which one I tried. try 12.1 first, however you feel like
once you have that follow the instruction of Gavtrain in his video to open the plugin in administrator and tadaaaaa it will work, it did for me