To set up Mac OS X to connect to a server at Login: Connect to the server you want to use. Open System Preferences. Select your account from the Accounts section. Click the Login Items tab. Drag the server's icon from a Finder window into the list of Login items in the System Preferences window. Quit System Preferences.
Assuming you do not have a backup/Time Machine archive of the Mac before it was messed up... Insert the Mac OS X installation disc and hold down the C key while the Mac starts up. This will boot the Mac from the installation disc. Undo what you did to change the Mac Login screen. You kept a copy of the original files didn't you?
If an application is opening every time your Mac is starting up click and hold on the application's icon in the dock. A menu will pop up with an Open At Login option. Select the Open At Login option so that it is no longer ticked.
When you remove an icon from the desktop on a Mac, you do not put the application in the trash only the desktop icon.
its the icon with the gears called system preferences
You have to change your Steam Nickname. It can be done in the Friends tab of Settings if you right click the icon in your taskbar. (Depends on Windows or Mac)
The Mail application will open if it has been set to open when you login. To reset this click and hold on the Mail icon in the Dock and a menu will pop up. Untick the option Open at Log In/Star Up.
The Mac Book Pro is better than the Mac Book Air.
Right Click The Safari Icon in the dock and UNcheck "Open at Login"
Of course you can make your "own" folder. You can even change the icon of the folder. If you need to know more just ask.