on Jan 4, 2019 at 2:59:39 pm Last Edited By Craig Seeman on Jan 4, 2019 at 3:06:24 pm
It depends on what your intent is with the resultant files. VirtualDub hasn't been updated in more than five years and doesn't support some of the "modern" codecs preferred in typical video post production workflows.
If you can access x264 encoder that might be a workable option but it would be .mp4 extension. Again it's not clear what your intent is. x264 wouldn't be my choice for post production work.
Install the free Lagarith .avi codec. Makes big files, but lossless quality. That is then your "master" of the converted file. From that .avi, create any deliverables like .mp4 then using other software such as ffmpeg