Developer Limitation Under SQL 2005 Under Vista Ultimate 64 Bit

Just to be clear, I would like to know if a problem I face is due to an error on my part or a limitation on Microsoft's. In my experience (several hours-long installations, removals, reinstallations, using the skuupgrade=1 parameter from the command line, ad nauseum) I have concluded that the best one can do installing SQL Server 2005 Developer Edition from the Visual Studio 2005 Professional Edition package is to get the Express Edition, (actually styled MSSMLBIZ). In particular, what I'm hoping to be able to do is program to a test database that I have from my client, which I was able to do on my XP Professional machine. But on my new Vista Ultimate 64 bit machine (which will only let me install the x64 version of SQL Server 2005), I get an instance that is characterized as SQL Server Express and generates the following error message when I try to attach to the same MDF file to which I was able to attach under my prior, XP-Pro based configuration:


TITLE: Microsoft SQL Server Management Studio
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Attach database failed for Server 'ZAPHOD42MSSMLBIZ'. (Microsoft.SqlServer.Smo)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=9.00.3042.00&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Attach+database+Server&LinkId=20476

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ADDITIONAL INFORMATION:

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

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CREATE DATABASE or ALTER DATABASE failed because the resulting cumulative database size would exceed your licensed limit of 4096 MB per database. (Microsoft SQL Server, Error: 1827)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.3054&EvtSrc=MSSQLServer&EvtID=1827&LinkId=20476

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BUTTONS:

OK
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The following is the Help obtained when clicking on the button on the error msg and the references in the error msg:
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Details
ID: Attach database Server
Source: Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText

We're sorry
There is no additional information about this issue in the Error and Event Log Messages or Knowledge Base databases at this time. You can use the links in the Support area to determine whether any additional information might be available elsewhere.


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Currently there are no Microsoft Knowledge Base articles available for this specific error or event message. For information about other support options you can use to find answers online, see http://support.microsoft.com/default.aspx.

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Details
ID: 1827
Source: MSSQLServer

We're sorry
There is no additional information about this issue in the Error and Event Log Messages or Knowledge Base databases at this time. You can use the links in the Support area to determine whether any additional information might be available elsewhere.
Thank you for searching on this message; your search helps us identify those areas for which we need to provide more information.

==========End of reproduction of error messages and help text ====================================

The Developer Edition, of course, is supposed to enable us to program to all levels of the database, and I would hate to think it is really crippled in this way, but after uninstalling everything, reinstalling multiple times (devoting several days to the process), it sure beats me how I can overcome this problem short of going back to my old machine. Any definitive answers on this apparent limitation, or useful procedural advice on installation quirks, would be appreciated (and, yes, I've spent a lot of time going through the installation/setup forum -- if the answer is there I can't find it).