I can't put files with effects into windows movie maker anymore.the old ones are likr normal video files and show a picture of the start but the new ones have a hand(the PI sign) when I look at them in folders
A file extension is the letters that follow the file name - so with a picture, it might be be "family.jpg." With a movie it might be something like "airplane.avi."
The file Extension indicates what kind of file it it is, so that the program you are using knows how to open the file, or even if it can or can't open it. - Photoshop, for example, can't open Avi's or quicktime Movies.
In your case, as far as I know, no other programs can open the IP3 or IPF format (ex: project_1.ip3, firball.ipf)- particleIllsuin 2 and 3's native format.
You have to render out a movie or an image sequence to use what you've done in pIllusion in a nother program.
And, before you ask how to do that... Do yourself a favor and read the help file tutorials. They will teach you everything you need to know to get started.