While setting the Output module settings to MPEG2, I get this message:
COULD NOT LOAD ANY WRITER. ADOBE MEDIA ENCODER WILL NOW EXIT. Upon
clicking on OK, I get this:
0 :: 9995
AFTER EFFECTS ERROR. WRITER INITIALIZATION ERROR.
Just like any of these errors - the software is not properly installed and/or was messed up by a third-party product (CoDec pack, alternate media players...) or by installing Encore/Premiere after AE. Sorry, but the only way to reinstate it is to uninstall and reinstall. Use the clean scripts from the Support site to get rid of all the remnants. Specific to Vista, also make sure to check for things like DEP, UAC and user permissions which may prevent the components from getting loaded.