Sorry about that Deena.  I hate it when people throw acronyms at me 
and now you have caught me doing just that.

AER is Archivos Españoles en Red 

Anyone can sign up for an account and they are in the process of 
digitizing (scanning) all of their collection and for those documents 
that have already been digitized, you can simply pull them up and 
view them online through the AER website:

http://aer.mcu.es/sgae/index_aer.jsp

I think the Sombrerete Padron that Joseph mentions is the following.  
If so it is not yet digitized, but you can probably order a hard copy.

Archivo  Archivo General de Indias  
Código de referencia  ES.41091.AGI/16403.15.1564//INDIFERENTE,1526  
Título  Padrones generales de los habitantes de Indias  
Alcance y Contenido  Padrones generales de los habitantes de Indias.  
Nivel de Descripción  Fracción de Serie-Unidad de Instalación  
Fecha(s)  [f] 1777  
Signatura(s)  INDIFERENTE,1526  
Volumen    1  Legajo(s) 
 
Productor(es)   Información de Contexto   
Notas  Signatura antigua: INDIFERENTE,145-7-5  
Índice(s)  Padrones de habitantes 



--- In ranchos@yahoogroups.com, "Deena Ortiz" <drortiz@...> wrote:
>
> I am very interested in knowing more about the "unfilmed" records 
of 
> Sombrerete.  You say the information should be available shortly 
via AER.  I 
> am not familiar with this term.
> 
> ~Deena Ortiz~
>