Type "Path" (without quotes) as the name of the new value, then press Enter.
In the right pane of the registry, right-click the (Default) value and choose Modify.
In the Value Data field, enter the location of the Photoshop.exe file on your computer. Include Photoshop.exe at the end of the path. For example, if you installed Photoshop CS5 to the default location, enter C:Program FilesAdobeAdobe Photoshop CS5Photoshop.exe. If you have a different version of Photoshop or have installed to a different directory, change the path as appropriate.