Encode x264 to smaller file size

[rjc7394]

I have a x264 file (1 GB; 34 minutes) which I want to make smaller (600 MB or so). I guess my format options are (1) Re-encode as x264 with lower bitrate or (2) Convert to XviD with lower bitrate (with same or different fps). I know how to convert to XviD and I tried that but how do I do option (1)? I installed AVIDemux, cut a 30-second segment to make a test run and chose a target file size but I really can't figure out how to start the encoding. Would I be better off just encoding it to XviD?

[Dark Shikari]

Try Ripbot264, Handbrake, Staxrip, or any one of the various GUIs around.