Nothing is free. If you don't want to pay to convert the avi to a vob file and set up a dvd from that then you are going to have to learn about it.
I suggest you try linux. Specifically -- and quite frankly -- I'm going to recommend here a distro I DESPISE (though I am a Linux user).
http://puredyne.org/index.html
Download the iso image and use one of these methods to install it to a 2 or 4 g usb stick:
https://wiki.ubuntu.com/LiveUsbPendrivePersistent
Reboot into your Linux system. Open a terminal and type "ls /media" without the quotes, then hit enter. If there is no directory listed then type "mkdir hd" or something, then ls /d2ev/sd*" look for /dev/sda" and /dev/sda1 /dev/sda2 whatever. If you just see /dev/sda then fine. Type "sudo mount -t ntfs /dev/sda hd". Now type "ls hd". Ls means list the directory in Unix and Linux. It should list the contents of your C:\ folder. If you got an error or there are other partitions try to mount /dev/sda1 /dev/sda2 or whatever. Each time run an ls. If you get an error and the directory is empty fine. Mount the next. If you get a different folder just type "umount hd" and you will get a differen folder. In any case, Once it is mounted, cd to hd, then cd to a directory with a lot of space -- you will need 3 -4 gigs of space for what I am about to recommend. You don't get that on the live cd. Anyhow the information is all on this page:
http://www.linux.com/news/software/multimedia/8250-convert-any-video-file-to-dvd-with-open-source-tools
I won't tell you why I despise pure dyne. It's not relevant. You should be able to use it -- it's an ubuntu derivative so I recommend following the instructions for putting Ubuntu on your flash drive. Don't follow theirs. I've never made them work. And yes, though I prefer other Linux distros I've made this work on Ubuntu. If you don't have a particular program they recommend type "sudo apt-get update" then "sudo apt-get install " and the name of the package you want to install. If it won't let you write to the disk, type "sudo su" and you will suddenly be root, able to write anything to disk or anywhere else that you want. When you reboot Windows may give you a hassle about these new files but screw it. My opinion of it is so low I prefer Pure Dyne. If your avi is on dvd then you can put it in and convert it to an mpeg -- the intermediate step -- remove it and put in the disk you want to burn. If you have it on the hard drive then convert and burn it and delete all the intermediate files you made. Then reboot and you will find that you wrote NOTHING to disk except what you specifically chose to.