I have a Poser file saved in my HDrive . have poser in my hdrive too. Well i just opened my poser file today, did no changes to it. Haven't made any changes to it in a lng time. all i was going to do is make a movie with the scene i have( 983 frames). so i did. and its not even rendered in full RENDER mode. it's Make movie with current display which is SHADED. and save the movie to an external drive. so it made the mov clip(.MOV in mac and used the ANIMATION compressor) but i got a YOUR START UP DISK IS ALMOST FULL message. then i look at my HD and sure enough IT ATE DISK SPACE i didn't know Poser ate disk space from Making amovie and moreover a movie saved to an external drive. What is that about? im in mac os X 10.4.7

I'm not sure how MacOS works but QuickTime in windows uses the main drive when it makes the MOVie file and then the OS moves it to the final destination drive once it's done.

It's been  a rule of thumb for me to make sure the drive that poser is on has enough free space to store the movie uncompressed; I've had graphics apps in the past that needed the space, as they rendered out each individual frame then compressed them into the finished product only at the end of the process. I have no idea if Poser or the Quicktime compressor work this way.
Also, if you are working with dynamics, both cloths & hair make pretty big temp files.

However, the last Apple product I touched was a new Lisa.