I am having lots of trouble understanding Excel references, or more
accurately how the various interfaces work.

When I open Excel I look in Tools | Add-Ins and I see that I have the
following Add-Ins ticked:

Analysis ToolPak
Analysis ToolPak VBA
Solver Add-in
VBA Code Cleaner 4.4

I open up the VBA editor and I see the following Add-in files opened:

atpvbaen.xls (ATPVBAEN.XLA)
funcres (FUNCRES.XLA)
VBACodeCleaner (VBACodeCleaner.xla)

QUESTION ONE - where is the solver Add-in? why is it not open?

In the VBA editor when I look in Tools references I see the following
ticked:

Visual Basic For applications
Microsoft Excel 10.0 Object library
OLE Automation
Microsoft Office 10.0 Object Library

I see the following but unticked (there are lots of others):

atpvbaen.xls
funcres
VBACodeCleaner

QUESTION TWO - Where is the Solver reference, even if it is unticked why it
is not show even?

QUESTION THREE - What does it signify when a reference appears above
unticked, even though it is ticked under Tools | Add-ins?

QUESTION FOUR (AND MOST IMPORTANT) - what is the relationship between the
Tools | Add-ins interface and the VBA Tools | References. If I add a
reference using: