Is the MPEG file MPEG2 (SVCD or other), if so then you can use DVD2SVCD to encode it. Just rename the file to VTS_01_1.VOB and extract a VTS_01_0.IFO off just about any DVD. Thats a simple dirty trick I use that ALWAYS works for me
If its MPEG1 (VCD or similar) then best would be encode direct to DVD using MainConcept MPEG Encoder. Going from MPEG to AVI to DVD looses to much and not advisable. MainConcept is good with VCD to DVDR with no visable loss in quality and its reasonbly quick. Just select DVD and stream type to be Elementry Video & Audio. Select audio mode to be WAV. It converts the 44.1khz audio to 48 automatically. You convert the WAV to AC3 ( ffMPEGGUI is good for that or the LATEST BeSweet) then just author in DVDLab, TMPGEnc DVD Author, Maestro or what ever.