Use Windows control panel to establish the file association.

This solution uses Photoshop as an example. For any other product, replace that product's filename extension and executable name with the product and file type you are attempting to restore.

Windows 7/Vista

1. Choose Start > Control Panels.
2. Change to list view:
3. Double-click Default Programs.

   4.  Click Associate A File Type.

   5.  Select .PSD from the list. 

1. Click Change Program.
2. If your desired version of Photoshop is listed, choose, it. Otherwise, click Browse to locate it and click Open.
3. Ensure the "Always use the selected program..." option is selected. Click OK to close the Open With dialog box.
4. Double-click an .PSD file to ensure that it opens with your preferred version of Photoshop.

• On Windows 7, click the View By pop-up menu and choose Small Icons.
• Windows Vista, click Classic View in the upper left.

Windows XP

1.        Choose Start > Control Panels > Folder Options.
2.        Click the File Types Tab.
3.        Select PSD from the list. 
   Note: If you do not have PSD in the list of extensions, skip ahead to the next section, Create a filename extension.
4.        Click Advanced.
5.        Select the Open action, and click Edit
6.        Click Browse and navigate to the Photoshop.exe for your version. Select it and click Open.
   Note: Make sure that the resulting value in the Application Used textbox has the following syntax, especially the "%1" (with quotes included). If it does not, manually edit the field contents so that it does:
   "C:\Program Files\Adobe\Adobe Photoshop CS6\Photoshop.exe" "%1"
7.        Select Use PSD and click OK to close the New Action dialog box.
8.        Click OK to close the Edit File Type dialog box.
9.        Click Close to close the Folder Options dialog box.
10.       Double-click an .PSD file to ensure that it opens with your preferred version of Photoshop.

----------------------------------------

How to associate files for Photoshop CS5 with Bridge CS5 and Photoshop CS6 with Bridge CS6

1. CS6 assigns all standard graphics files to be associated with CS6 and thus causes Bridge CS5 to invoke Photoshop CS6.  The objective is to have Bridge CS5 invoke Photoshop CS5 at least for chosen file types.  Ensure neither CS5 nor CS6 is invoked.

2. In the Win7 Start Menu search box, type "file association".

3. Select the "Change the file type associated with a file extension".  This starts a window titled "Associate a file type or protocol with a specific program".

4. All of the graphic files are assocated with Photoshop CS6.   For those files you want to associate with Photoshop CS5, click on the chosen file extension (e.g. .cr2, .nef, .psd, etc) and click on the "Change Program" to associate the extension to Adobe Photoshop CS5.  (note.  this step seems to be a necessary operation since, when I simply modified the Bridge CS5 file type associations, Bridge 5 did not honor the change).

5. Start Bridge CS5. Choose "Edit -> Preferences -> File Type Associations".

6. For each file type you wish opened in CS5, change the association from CS6: choose the "Browse" option and locate the CS5 version of Photoshop.exe".  This is probably in Program Files/Adobe/Adobe Photoshop CS5 (64 Bit)/Photoshop.exe. Click on OK to complete the association.

Now you can invoke Bridge CS5 and it will properly invoke Photoshop CS5.  If you invoke Bridge CS6, it will invoke Photoshop CS6.  If you use file manager to invoke one of your selected file extension types, it will start Photoshop CS5. Other graphic files will start Photoshop CS6.

If you wish, you can go back and reassociate the chosen types to PhotoshopCS 6 - but your Bridge 5 will still invoke PS5 for your chosen extensions since the Bridge-assigned file associations takes priority over the windows default program.