Hi wondering if anyone could answer these few questions for me.

1 ) How can i use a password system with php?. i mean so that i can create an account and it saves it in a database. i have a basic idea after reading the tutorial on webmasterbase but would like some more pointers if possible.

2) How do i make it so people can upload certain files. Like i dont want people to upload .zip files how would i do this feature. id like to be able to edit these from an admin panel too.

thanks for any help given :-).