I regularly download a large variety of text-based files using Firefox. Most of the time, I want to open these using Notepad++. Previously, after I'd opened the first file using Notepad++ (selected via the Browse... button), the application would show up in the 'Choose Helper Application' list. However, I've recently replaced my PC, and this no longer happens. Now I need to click Browse... and navigate through the file system every time to find Notepad++.exe, which is wasting time.

Please note I'm not talking about associating file types - as mentioned there are a lot of different file types, and I just want Notepad++ to show up in the menu list.