Help - Error: Unable to open the physical file

Hi, I've just finished creating my first ASP.NET website. I created it on my laptop and it works perfectly, but I'm having some problems deploying it to my web server (PC).
The site works ok, but when I try to log in to my client area, I get this error:

"Unable to open the physical file "c:\inetpub\wwwroot\ONeillStrata\App_Data\aspnetdb.mdf". Operating system error 5: "5(Access is denied.)".
An attempt to attach an auto-named database for file c:\inetpub\wwwroot\ONeillStrata\App_Data\aspnetdb.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share."

I've searched far and wide for a solution and have read many articles, but none seem to be able to fix my problem. I've tried using that SEUtil tool, but that didn't work, I've made sure the App_Data directory on the web server isn't read only (the read-only checkbox isn't ticked, but it DOES have that little green square which I can't get rid of), I've assigned the ASPNET user as a db owner and that didn't work and I've manually attached the database to the web server's instance of SQL Express 2005.
When I launch the solution in VS2005 on the web server, I can browse through the database and see the tables and data etc, but when I try to run the application, I get that message above...

Surely it shouldn't be this hard to get it going?
Any help would be massively appreciated.

Hi,

It seems that the physical file location of the aspnetdb.mdf is wrong.

Please open your IIS, right click on your default web site,and click on the properties, change to the ASP.NET tab, edit configurations.Then you can see the LocalSqlServer string listed there, change the string into the following:data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true.

Thanks.