Hardware connection

Hi there all,
I've just bought a HP A6250 pc and a HP W2207H monitor 22" and I've fixed
them together, why do I need to use three connectors?. One is the old style
port connection, one is USB and the other is sound connection. Why all three?
oh and another thing when unpacking and setting up the monitor stand it was
incredibly stiff to pull the screen in to the upright position I thought at
one stage that any more force and the thing would break, but after it started
to move it SLOWLY came upright...just a warning for those who think that the
stand has been put on 90 degrees out...like I did for 10-15 minutes
--
Ralph