Configure The Membership In ASP.NET?

i need to set up membership for my first website, as i was told i have followed the following steps:1. website --> ASP .NET configuration2. select teh security tab If my admin tool works fine , then it should display the following

1. users - allows to create and manage users2. Role - enable roles3. Access rules - create and manage access rules But my security tab doesnt display those otpions instead it displays an error as:

Code:"There is a problem with your selected data store. This can be caused by an invalid server name or credentials, or by insufficient permission. It can also be caused by the role manager feature not being enabled. Click the button below to be redirected to a page where you can choose a new data store.

The following message may help in diagnosing the problem: An error occurred during the execution of the SQL file 'InstallCommon.sql'. The SQL error number is 1802 and the SqlException message is: CREATE DATABASE failed. Some file names listed could not be created. Check related errors. Cannot create file 'C:VBWEBSITESMEMBERSHIP1APP_DATAASPNETDB_TMP.MDF' because it already exists. Change the file path or the file name, and retry the operation. Creating the ASPNETDB_dbd9891837cf479eab2e5e8a5e483986 database... "

Then i followed it's instructions, clicked on choose datastore and configured the provider, according to the web admin tool the "single provider" passed the test.

Then i closed the adin tool and restarted it. but still the above error occurs. How can i fix this? PS: this happens even when i disable the firewall!