SQL Server Management Studio 2012 ERROR 916

Hi to All.
My scenario is:
PC1 (local): Windows 7 x64, SQL Server Management Studio 2012, one instance of SQL Express 2012, named 'AUTOPID' accessible via '(local)\AUTOPID'.
PC2 (name:VSDS20): Windows server 2008 R2, one instance of SQL Express 2012, named AUTOPID accessible via 'VSDS20\AUTOPID'
From PC1 I am able to connect to VSDS20\AUTOPID. Once connected I see the node named 'database', right click on it and select New database. The form for creating the database is opened and enter the database name 'testdb', click OK and then an error window comes out with this message: 
CREATE DATABASE permission denied in database 'master'. (Microsoft SQL Server, error: 262)
If I try to connect a database another error comes out: The server principal "VSD\luigi.ballotta" is not able to access the database "model" under the current security context. (Microsoft SQL Server, error: 916).
Same behavior ru ...