Yes I'm using a simple text editor (not notepad). Various program will even cull out everything but the ascii text for you. Text scaps seems to be more prevalent with unfinished mp3's than anything else. I have previously noticed when viewing an unfinished movie an unrelated movie downloaded earlier sometimes plays a few frames at the end. The size of the .dat files is partially dependant on how quick you pause the download after starting it. Kazaa seems to have a minimum file chunk of 100kb (at least in my samples) even if you haven't actually downloaded that much yet. That probably explains why it is happening since any deleted file/s contained in that space will once again be designated as being part of a particular file. A little more forensics could reveal a lot more. A few attempts with other file types revealed no text, but out of six mp3's they all had at some recognizable text from other files.
Gravity, the .dat files and the movie files are the exact same file. Kazaa simply gives them a .dat extension until the download is finished. that wouldn't be any help to the dialup users. I downloaded for my friend then physically carried the files back to her computer when finished. USB memory is pretty cool.