Can't Attach Adventure Works OLTP mdf File to SQL Server 2012 Express

Hi All,
I have installed SQL Server 2012 Express on my windows Vista machine and have the Adventure Works OLTP mdf file.  When I try to attach the file either with a script or locating the file, I get an access denied error.  I am logged onto the computer as an Administrator.  Can someone tell me how to get pass this?
Thanks,
crappieCal 
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