Use Sp_configure Error.what Is This?

 Hi,
i am using vwd2005 express and sql express.
i have downloaded a web application and trying to run it.   
But when i run this application its showing some error in the page. like this:-

Server Error in '/ProfileSample' Application.

Generating user instances in SQL Server is disabled. Use sp_configure 'user instances enabled' to generate user instances.



Description: An
unhandled exception occurred during the execution of the current web
request. Please review the stack trace for more information about the
error and where it originated in the code.



SQLExpress database file auto-creation error:


The
connection string specifies a local Sql Server Express instance using a
database location within the applications App_Data directory. The
provider attempted to automatically create the application services
database because the provider determined that the database does not
exist. The following configuration requirements are necessary to
successfully check for existence of the application services database
and automatically create the application services database:

If the applications App_Data directory does not already exist, the
web server account must have read and write access to the applications
directory. This is necessary because the web server account will
automatically create the App_Data directory if it does not already
exist.If the applications App_Data directory already exists, the web
server account only requires read and write access to the applications
App_Data directory. This is necessary because the web server account
will attempt to verify that the Sql Server Express database already
exists within the applications App_Data directory. Revoking read access
on the App_Data directory from the web server account will prevent the
provider from correctly determining if the Sql Server Express database
already exists. This will cause an error when the provider attempts to
create a duplicate of an already existing database. Write access is
required because the web server accounts credentials are used when
creating the new database.Sql Server Express must be installed on the machine.The process identity for the web server account must have a local user profile. See the r But same application is running well in my friend system.
I dont know whats wrong here.
does anyone has a answer?
Thanks.
Jack