Trimming a video in Sony Vegas

I've tried trimming a large video file in Sony Vegas Platinum 11.0 with the intention of eliminating part of the file, i.e., reducing its size so it does not occupy as many gigabytes of hard disc space. I use the 'Split' function to do this. However, what happens is that a second file is created, much smaller in size, that apparently is a shell that just turns the original file on at a certain frame and off at a certain later frame. So I have more, not less, storage space taken up. Does anyone know if a 'true' trimming can be done that actually makes the original file smaller in size, and, if so, how to do it? I'm doing this on a VAIO SVS15118FXB laptop running Windows 7 x64.