from the divx_editing page:
Here are some formats which are fine to edit with:
* Uncompressed (file sizes can be very large, though)
* Huffyuv (smaller than uncompressed, but still huge)
* Lagarith (smaller still than HuffYUV, but is slower)
* DV (this format will introduce some slight quality loss into your video, and also has some restrictions on resolution and framerate)
* M-JPEG (depending on the quality level you set, it can be large, and can introduce slight to significant quality loss, however it is very fast)
* AVISynth (doesn't involve making a large file, but can be slow and is not supported well by all editing software)
[and a little further down the page]
More Complex Way
If your video is in AVI format, and you have the appropriate Video for Windows codec (true if you can open the file in VirtualDub without error), you can serve it via an AVISynth script with the following line:
(replacing the path and filename as appropriate, of course).
If the file is not an AVI file, or if the above line doesn't work, then you can try the following line:
Once you have the file loaded through AVISynth, you can either load it directly into your editing program (if it supports AVISynth scripts), or you can load it into VirtualDub where you can encode it into another codec such as Huffyuv or Lagarith.