Default HEC-RAS Version

This was driving me ever so slightly nuts for a little while. I’ve had HEC-RAS 6.4.1 on my work laptop (Windows 10) and recently installed version 6.5, too. Previously I set my machine to open .prj files with HEC-RAS 6.4.1. I’ve been wanting them to open with version 6.5 by default, but no matter what I did they were still opening with 6.4.1.

I figured there was probably some system registry setting that would allow me to set .prj files to open with HEC-RAS 6.5 instead. I’ve been leaning heavily on ChatGPT for technical issues like this to avoid digging through documentation and StackOverflow answers, and it didn’t disappoint.

Here are the instructions ChatGPT landed on after a couple rounds of back-and-forth…

Step-by-Step Instructions:

1. Navigate to UserChoice Key:
   • Go to:

     HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.prj\UserChoice
     

2. Change the ProgId:
   • In the UserChoice key, find the ProgId. This tells Windows which application to use for opening .prj files.
   • Since the ProgId is currently set to prj_auto_file, you need to ensure that this is linked to the correct executable path in another part of the registry.
3. Modify the Default Program in prj_auto_file:
   • Go to:

     HKEY_CLASSES_ROOT\prj_auto_file\shell\open\command
     

   • Check the default value here—it should be pointing to the executable for HEC-RAS. This is where you can specify the path to the new version of the application. If this key does not exist, you will need to create it.

Create or Modify the Command Key:

If the path needs to be updated or created, follow these steps:

1. Navigate or Create Keys:
   • Go to HKEY_CLASSES_ROOT
   • Look for a key named prj_auto_file. If it doesn’t exist, you need to create it by right-clicking on HKEY_CLASSES_ROOT, selecting New > Key, and naming it prj_auto_file.
   • Within prj_auto_file, create a new key named shell if it doesn’t exist.
   • Inside shell, create another key named open.
   • Within open, create a final key named command.
2. Set the Default Program:
   • In the command key, double-click the default value and change it to:

     "C:\Program Files (x86)\HEC\HEC-RAS\6.5\Ras.exe" "%1"
     

   • %1 allows the program to receive the file as an argument.

Apply Changes and Test:

• Close the Registry Editor.
• Restart your computer to ensure the changes take effect.
• Try opening a .prj file to see if it opens with the correct version of HEC-RAS.

Note:

This is a sensitive process, as incorrect changes to the registry can cause applications or the system to behave unexpectedly. If you’re not comfortable doing this, it might be wise to consult with an IT professional or someone familiar with Windows system administration.