MapiExceptionCallFailed: Unable to mount database. (hr=0x80004005, ec=-2147467259)

This solution is with regards to the following error message. Unfortunately now I am running all my software in spanish so the error code is half in Spanish and half in English. This error is generated when you try to mount a database in Exchange 2007 right after you are done installing. The Public Folder Database works fine though.

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Microsoft Exchange Error
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No se pudo montar la base de datos "Mailbox Database".

Mailbox Database
Error
Error:
Exchange no puede montar la base de datos especificada. Base de datos especificada: ServerNameFirst Storage GroupMailbox Database; código de error: MapiExceptionCallFailed: Unable to mount database. (hr=0x80004005, ec=-2147467259)

In order to resolve this issue follow the steps on KB925825 at http://support.microsoft.com/kb/925825/en-us

I've seen some issues with people trying to run Setup /PrepareAD as it will indicate the following message:

C:Usersusername>Setup /PrepareAD
Welcome to Microsoft Exchange Server 2007 Unattended Setup
Preparing Exchange Setup

Exchange Server setup encountered an error.

This is due to the fact that you are not running the command line as an Administrator. Remember that in Vista and Windows 2008 you must run CMD as an administrator. Right click the Command Prompt shortcut and select the Run as Administrator option before you try to prepare AD.

I would also suggest you take a look at the help for preparing AD for an Exchange 2007 installation. Here is an extract from the KB on how to do that:

Click the Contents tab, expand Deployment, expand New Installation, expand Preparing to Deploy Exchange 2007, and then click How to Prepare Active Directory and Domains.

Finally, I also found that this is the sequence you want to follow to prepare your AD for deployment:

1. Setup /PrepareSchema 
2. Setup /PrepareAD

I had done the /PrepareSchema but missed the /PrepareAD. Once I did that I was able to mount the store. Good luck to everyone!