There is a common misunderstanding that because Betaplayer can parse the Quicktime container format that it can also play the contents, this is not the case. Sorenson video is not supported by Betaplayer (neither is the QDesign Audio Codec which is also common in MOV files) and according to Picard probably never will be.
To convert such a video requires a 2 step conversion process as Quicktime for Windows has pretty poor AVI support. The huge file that you got from your first conversion attempt is most likely an Uncompressed AVI which is the first step. Take that file and recompress it to DivX, XviD or MPEG1 with a tool like VirtualDub or Dr. Divx, this will produce a file that is both small and compatible with Betaplayer. Most video compression questions can be answered by heading over to
VideoHelp.com and taking a look through the guides section.