Customizing different user accounts.

Hi,
I just got my computer and am trying to set up 3 different profiles. I am
running into a few problems. Here they are:

1. I want to allow Windows Live Messenger in one of my non-administrator
accounts but not in any of the others. I would like to know if I can set up
each account to have different programs from the other and how to install
programs like Windows Live Messenger in just one profile if I want to.

2. For my kids account I have disabled acess to most programs, but now when
that account logs on about ten different startup programs start and are not
allowed. I do not know how to disable these programs for that account.

3. This ties into my last problem. I want to know which programs (ie.
network magic, Corel Photo Downloader, Message Center, etc.)are necessary to
have running on startup (ie.what they do) and how to safely remove them if I
dont need them.

If you have any help for me or know where I can get detaied info. on these
things I would sure appreciate it.

Thank You,
Soso