Ok, on the front end, this problem involves XviD, somewhere on this forum I saw someone get scolded for mentioning XviD or DivX, so please, I only mean well and I really want some help here so just point me in the right direction.

Ok I have an XviD format video at 25 fps, and I want to convert it to KDVD Full D1, I've followed all the steps, and the place where I have my problem is jumpy video after encoding using TMPGenc. Through experimentation I have found that TMPGenc does not cause the video to be jumpy if the framerate is 23.976 as per KDVD Full D1 settings. If I try to change the framerate in VirtualDub, I end up with two BAD results:

1.One is where the video length is the same, the framerate is changed, the motion in the video is perfect except for every five seconds or so there is a very noticable jump in the video.

2.The second one is the video plays back with NO jumps and looks very good and is at 23.976 fps which TMPGenc converts without a hitch, the only problem is the video is about 1 minute and 57 seconds longer.

Please help me, I've tried dabbling in AVIsynth, but gaully it seems way over my head. What is the most concrete solution to create a smooth video of the same length going from 25 fps to 23.976??? Thank you!

You can't. But you don't have to neither. If your source is 25, the you have to encode it in 25.

Do you mean that you are in a NTSC region and your material do not support PAL framerate ?
If yes, then still encode in 25 and use DGPulldown to "tweak" the video to a correct NTSC framerate (that is 29.970 and nothing else for a DVD !!!).