I have never tried running .NET 1.1 based applications on Windows 10/11. Microsoft does not support it, but googling shows some ways around it:
I have not tried it myself, but it might work for you.
EditVoicepack XL does have some limited capabilities to update FS2004, but please notice the following limitations:
- It requires FSX or P3D installed. So it is not free
- It is applying the FSX voicepack to FS2004 (with a few syntax modifications), and I have not spend a lot of time testing this – so definitely use the trial version to check it is good enough for what you want before buying a license.