Codec : choose wich one you want to use using using the dialog box :
if you're not familiar with advanced Divx or Xvid paramteres, just checked the Use Auto Codec Calibration checkbox and Aspirator will manage the codecs configuration. Even if you use this feature you can edit advanced parameters using the See Codec push button.
Low Space mode : you can choose between a low space mode (only 2 gigas of free hard disk space needed ... ). For that use the miscellanous box :
Remember that if you make a 2 passes movie, the DVD 'll be read twice, so Low Space Mode Processing is a bit longer thant a Non Low Space Mode. Anyway somtimes it's easier to waste a littlle more time than to free 5 or 6 gigas of your hard drive.