In the amount of time it took you to sign up to this forum, you could have went to the tutorials page,
http://www.xbox-scene.com/tutorials.php, and answered your own questions. Do some research!
A stock X-Box comes with an 8GB drive (some reports of 10GB). You can NOT use CD-RW's until your box is modded. You can NOT swap to a bigger hard drive without a mod chip.
XBox Media Player, X-Mame, xSnes9x, etc., etc., all require you to be able to run unsigned code. Guess what it takes to run unsigned code? A MOD CHIP!
Once you are modded, YES, you can manage your filesystem using applications such as boXplorer, or by FTP'ing to your X-Box using Evolution-X.
Hopefully that answers your initial questions. Is the X-ecuter right for you? That depends... Do you have a need to flash the BIOS? Can you solder? Is the X-Box you got a version 1.0 or 1.1 (again, refer to the tutorials to determine this). If it's a 1.1 box, Sorry, No X-ecutor for you!
Now, grab the mouse and start clicking and reading!
Don't at all mean to flame you, but every question you have, and questions you have not even thought of are already outlined on this site...
cent