Avi to dvd? dvdsanta and vista home premium?

i have dvdsanta 4.50 and im running windows vista since i upgraded to vista all of my output files are not encoding right. i am getting like 2GB instead of the 4.3GB i need to know it is good quality. any ideas ppl. or if anyone knows of a good programme toencode aci files to eather dvd or vcd thanks guys.