WinXP Pro User Administrator Account vs The Administrator

I'm trying to understand the User Accounts better so that I can unclutter
and organize the WinXP Pro file structure. I am getting dizzy trying to
answer my question in WindowsXP InsideOut. It has good information but I
seem to be going around and around.

I have 3 User accounts:
Grandpa (renamed from 'Ken') (has a password of, say, 'pw')
Kids (new account)
Guests (new account)

Under C:\ I have the following folders:
Documents and Settings\Administrator\Administrator's Documents
Documents and Settings\All Users
Documents and Settings\Default User
Documents and Settings\Guest\Guest Documents
Documents and Settings\The Administrator\My Documents

Then under 'My Computer' I have:
Shared Documents
Guest's Documents
Grandpa's Documents

Then under 'Desktop' I have:
Terrie (a User Account that I had deleted)

Over time, I have saved files, installed programs, etc. and have information
in both the 'The Administrator' and the 'Grandpa folders.

When the computer boots, and goes to the Welcome screen, I can select
'Grandpa and it asks for my password of 'pw'. However, if I instead do
Ctl+Alt+Del twice to get the main (undeletable)Administrator account, it
also asks for the password and 'pw' works there also. *Question* Have I
somehow re-named the main (undeletable) Administrators account? Or, is the
'The Administrators' folder a 'User Name' (WindowsXP book talks about 'User
Name' and 'Full Name'?) I had put in there from long ago? I'm really
confused. Why two administrator account folders: 'Admiinistrator' and 'The
Administrator'?
Thanks for your help