Hey valtea...
The thing is as follows:
As far as series 60 phones are concerned, the following are the drives and their meanings:
C: -> Phone Memory
The memory that resides on the phone... Comes default
D: -> Ram Drive (Temporary Memory)
The memory that resides on the phone... Comes default.
This is temporary memory used to buffer data when you are downloading via gprs, etc...
E: -> Memory Card (RS-MMC, DV-MMC, SD etc...)
The memory that resides on the memory card.
Z: -> System ROM
The part of read only memory which contains your symbian os. This is from where the OS and applications are loaded into the memory when the phone boots up.
As far as the folder structure goes, this is it:
C:\Cache -> Contains cache data during browsing, transfers etc.
C:\Documents -> similar to My Documents in windows. Contains your document files that you make....
C:\Nokia -> Contains sub folders namely Games, Images, Installs, muvee clips, Others, Sounds, Videos: These are folders predefined by symbian for the purpose that is clear from their names. Games folder saves games, images folder contains images taken from camera etc....
C:\System -> This is the main folder containing the files of applications that are installed / loaded when your OS boots....
This is the most important folder. If u notice, inside this folder, you will have a folder called apps where all your applications installed on phone memory are stored.
Another folder called Data exists which stores all the data files that are created when your application is running... Something like temporary / permanent store...
Another folder called Mail exists which stores all your Messages content - email, sms etc...
Libs is the folder where all your dll's that are part of applications are stored....
Thats all that i can think of now..
Do catch up if you have any more clarifications....