personal settings

How do I go in and change what programs load when I log
in. The problem I have is that some of the programs my
son has start under his user account automatically start
when I log on and I don't want them to. Also how can I
lock my internet settings so that my home page will not
change unless I change it myself? Right now every time
the computer is restarted it resets my home page to a
page that loaded itself when my son downloaded some kind
of free software.

Steve