for general data burning i recommend the FREE application called ImgBurn (www.imgburn.com) and set it to MODE > BUILD and just add in your files and setup burning speed (i recommend 8x in general for DVD's to keep quality good) then burn it.
and on it's 'OPTIONS' tab (when your in the MODE > BUILD section) i recommend switching the 'file system' to "ISO9660 + Joliet + UDF" for general data backup.
p.s. main reason i suggested the switch from the default of "ISO9660 + UDF" to "ISO9660 + Joliet + UDF" is that some things (like XBox console running XBMC) will have the file names cut off to 8characters etc etc if you dont do that which can be annoying since your file names wont be named like they should be.
for example... you name a file 'MyXviDMovie.avi' and burn it with the defaults (i.e. 9660 + UDF) and then try playing it back on a XBox running XBMC it will show up in it something like "MYXVIDM~.avi" ... which as you can see is annoying and does not look professional at all.... where as with the change (ISO9660 + Joliet + UDF) it displays the way it supposed to be (i.e. exact the way you named it )
but if your talking about converting .avi to standard DVD format so they can play on all dvd players then i cant help you much since im not a big fan of converting .avi to dvd as i prefer the other way around (dvd to .avi) as you can fit alot more movies (3 to 6 films to be exact) to DVD+R discs that way.