sandro7:

I assume that you're using BIAB for WINDOWS since you're on this Forum, also that you're using Version 2016, build 432.

I opened a song, then used File > Save Special > Export as MP4...
I navigated to a folder that I knew I could find, typed in a file name and clicked Save.

In the bottom RH corner of the screen I get a yellow box that says Rendering file .....

When the rendering is finished, I get another yellow box that says "Error: Quicktime for Windows not installed...."

When I go to my folder I find, along with my original BIAB .sgu file, I have a .bt1 file and a .WAV file.

I assume that means that I would have to have Quicktime installed in order to get an MP4 file.

Can you please try the above and let us know what folder you're saving to, and what you find there and any "yellow box" messages you might get along the way?

Good luck!
LLOYD S