Unfortunately, we do not know about any doable stp to avi conversion at this time or what it might be useful for. STP format generally contains CAD/3D model data and AVI is video, so unless this is something highly special it might not be actually possible to convert stp to avi.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.