How do I associate all unknown file types with notepad++?

I work alot with billing and files the bank etc. send me files that have date extensions or some counter as an extension:

eg file1.20110315 or file2.123

So the extension changes every time I receive another file.

Is it possible to associate all file types that end in numbers or if not any unknown file types with notepad(++)?

Thanks

You can edit the openas command of the Unknown type, i.e.

HKEY_CLASSES_ROOT\Unknown\shell\openas\command.

Alternatively, you can add a new command if you want to keep the Open As command.

If you want to make Open with Notepad++ the default, edit the default value of the HKEY_CLASSES_ROOT\Unknown\shell subkey.

As the accepted answer isn't explicit in how to do this, here's how I got it to work:

1. Open regedit.exe as administrator
2. Navigate to HKEY_CLASSES_ROOT\Unknown\shell
3. Right-click shell -> New -> Key -> "npp"
4. Right-click npp -> New -> Key -> "command"
5. Edit the Default value of npp\command to be C:\Program Files\Notepad++\notepad++.exe "%V" or "C:\Program Files (x86)\Notepad++\notepad++.exe" "%V" depending on where you installed npp.
   (The %V passes the file path to the program).