virtual directory not being configured as an application in IIS

Hello,
I am trying to open web project and run it. When I am going to run it the following error arises. I have already configured the web.config file of this project as per my system, but still this error occurs.
It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS.
Here is my web.config file

<?xml version="1.0"?>
<!--
    Note: As an alternative to hand editing this file you can use the
    web admin tool to configure settings for your application. Use
    the Website->Asp.Net Configuration option in Visual Studio.
    A full list of settings and comments can be found in
    machine.config.comments usually located in
    \Windows\Microsoft.Net\Framework\v2.x\Config
-->
<configuration>
    <appSettings/>
    <connectionStrings>
        <add name="HelpDBConString" connectionString="Data Source=ALOK-PC\SQLEXPRESS;Initial Catalog=HELPDESKMGMTSystem;Trusted_Connection=true;" providerName="System.Data.SqlClient"/>
    </connectionStrings>
    <system.web>
        <!--
            Set compilation debug="true" to insert debugging
            symbols into the compiled page. Because this
            affects performance, set this value to true only
            during development.
        -->
        <compilation debug="true" targetFramework="4.0">
        </compilation>
        <!--
            The <authentication> section enables configuration
            of the security authentication mode used by
            ASP.NET to identify an incoming user.
        -->
        <authentication mode="Windows"/>
        <!--
            The <customErrors> section enables configuration
            of what to do if/when an unhandled error occurs
            during the execution of a request. Specifically,
            it enables developers to configure html error pages
            to be displayed in place of a error stack trace.
 
        <customErrors mode="RemoteOnly" defaultRedirect="GenericErrorPage.htm">
            <error statusCode="403" redirect="NoAccess.htm" />
            <error statusCode="404" redirect="FileNotFound.htm" />
        </customErrors>
        -->
        <pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID"/></system.web>
    <!--
        The system.webServer section is required for running ASP.NET AJAX under Internet
        Information Services 7.0.  It is not necessary for previous version of IIS.
    -->
</configuration>

 
and the error is-

Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.
 

 
What should be the solution of this error. Pls tell me...
Thank you.