File > Save is designed to save changes made to an existing saved file on the hard disk.
File > Save As lets you create a new file on the hard disk.
in many programs, if you go Save, but don't have a hard disk file yet, then you get redirected to the Save As function, and shown the window where you pick your filename and folder. in anim8or, that doesn't happen. when you've started work on a new project, File > Save is disabled because the project exists only in the RAM so far, there's no file saved on the hard disk at all to start with. that's why you're forced to use File > Save As, that's the one which lets you put your file onto the hard disk for the first time. once you've done that, Save will become enabled, and you can use it to save further changes to the project.
(hope that's not too technical... i did 2 years' worth of Computing a-level, so i sometimes get a bit carried away with the inner workings of the machine - please forgive me if i sound like i'm talking double-dutch!
)
anyways, i think the default save folder for .an8 files is the same as whatever folder anim8or itself is in - i think C:\Program Files\Anim8or is the recommended one. there's no need to change folders, just give it a name, and save.
- colclough