if they're not XviD or SVCD, i wouldn't even attempt to even do it.
www.doom9.org has all the info you need for that.
basically in a nutshell
convert with tmpgenc all your video files to NTSC VCD.
use tmpg dvd author to make your menus, layouts, etc.. have it author your dvd.
use nero to burn it. dump all the files where it authored to inside the VIDEO_TS folder of your dvd.
in my opinion, DVD burning isn't worth it. you need your video formats correct. some people encode video as NTSC some as PAL. when you think you have all your videos converted, the dvd authoring program tells you its gotta be all NTSC or all PAL.
so there goes another few hours of encoding... you get everything ready. now you author.. that takes about an hour.
you burn. its good.
i could of burned 2 SVCDs in under 10 minutes.