> I am now trying to use it in command-line mode by writing 
> commands to a .bat file from VB6 and executing it using 
> CreateProcess. It starts WinHTTrack, but stops 
immediately 
> with 'File not found' error.

Ensure that ALL paths are absolute (even -O <paths> ones), 
this should do the trick. Also ensure that you don't need 
to escape paths using quotes ("")