I simply renamed the batch file to FiddyStartup.bat (no spaces) and it ran fine at the end of the Fidelizer startup process, so I'm not sure what you're referring to. It's definitely a problem with the way Fidelizer handles spaces. I bet if I renamed foobar2000.exe to "foobar 2000.exe" it would fail to launch.
Anyway, all that's left for me to do is figure out how to get the command prompt window to either close once foobar2000 launches (last step in the batch file), or hide it. nircmd works well for that when I used it in testing just starting foobar2000. Maybe the echo statements are the problem.
OK, never mind about renaming foobar2000.exe, cuz that just breaks it
After lots of experimentation here's the problem I have with Fidelizer launching a batch file upon completion: the command prompt window always stays open. I even tried converting the batch file to a .exe, but still ended up with a window I have to close. In the end, the easiest solution for me - the goal being to restart DWM, TightVNC, and launch foobar2000 into a specific playlist and have it start playing... with no visible command prompt window - is to stick all three operations in a batch file, tell Fidelizer not to start anything, and run said batch file manually. Again, it's just what works best for me. Fidelizer will do all that, if I tell it to run the batch file, I just don't want to have to close that window.
Picking at nits, to be sure, but there ya go.
If you have any suggestions as to how to get that command window to close after Fidelizer runs it, I'm all ears. If not, it's all good