and as quick as a flash google found theses
Error "Could not find Acrobat External Windows Handler" occurs when you view a PDF file (Acrobat and Adobe Reader 4.x-5.x on Windows)
Issue
When you try to view an Adobe PDF file in a web browser, Adobe Acrobat or Adobe Reader returns the error message, "Could not find Acrobat External Windows Handler."
Solutions
Do one or more of the following solutions:
Solution 1: Remove all versions of Acrobat or Reader, and then reinstall one version.
If multiple versions of Acrobat or Reader are installed on the system, remove all versions and then install only one version. See the documentation included with Windows for information about removing programs.
Note: If you need to have multiple versions of an Acrobat product installed, remove all versions and then reinstall them starting with the earliest, installing the latest version last.
Solution 2: Start Acrobat or Reader, and then open the PDF file in the web browser.
If an error occurs when you try to start Acrobat or Reader, refer to Related Documents below, or search the Adobe Support Knowledgebase:
-- If you use Acrobat, go to
www.adobe.com/support/products/acrobat.html .
-- If you use Reader, go to
www.adobe.com/support/products/acrreader.html .
Solution 3: Make sure that the External Window Handler file (ewh32.api) is in the Plug-ins folder.
If this file is missing, reinstall Acrobat or Adobe Reader.
The default location of the Plug-ins folder is:
-- For Acrobat: Program Files\Adobe\Acrobat [version] \Acrobat
-- For Reader: Program Files\Adobe\Acrobat [version] \Reader
Solution 4: Disable Web Browser Integration.
Disable Web Browser Integration so that PDF files open directly in Acrobat or Reader instead of in the web browser.
To disable Web Browser Integration in Acrobat 6.0.x -7.0.x or Reader 6.0.x -7.0.x:
1. Open Acrobat or Reader.
2. Choose Edit > Preferences > Internet.
3. Deselect Display PDF in Browser.
4. Click OK.
To disable Web Browser Integration in Acrobat 5.x or Acrobat Reader 5.x:
1. Open Acrobat or Acrobat Reader.
2. Choose Edit > Preferences > General.
3. Click Options in the list in the Preferences dialog box.
4. Deselect Display PDF in Browser.
5. Click OK.
To disable Web Browser Integration in Acrobat 4.x or Acrobat Reader 4.x:
1. Open Acrobat or Acrobat Reader.
2. Choose File > Preferences > General.
3. Deselect Web Browser Integration in the General Preferences dialog box.
4. Click OK.