My desktop is saying I have 100.0 mbps speed, but my laptop (broadband wireless
Between them and the internet) only connects at 6.0 mbps - what is wrong?
Also, what is the difference between 1.5 mbps satellite dish and 100.0 mbps broadband?

Sounds about right, although the wireless report does seem on the very low side.
What's your signal strength like?

These figures represent your computers connection to you broadband ROUTER and not the internet itself.
You internet connection speed will be something else entirely.

You mention a 1.5 mbps sat connection, that sounds like you actual internet connections top speed.

The 100mbps is in reference to your NIC's attainable speed and the speed of transfer inside your LAN. This has nothing to do with the internet.

Your internet is probably 56k, 1.5 mb, 3 mb, 5mb, or 10mb. Maybe more maybe less! Who knows! But it's not 100 :(