First, you need to configure IIS to run 32-bit Web applications on 64-bit Windows, then you need to register the ASP.NET application, then restart the Web publishing service.
To enable IIS 6.0 to run 32-bit Web applications on 64-bit Windows
Open a command prompt and navigate to the \Inetpub\AdminScripts directory.
Type the following:
cscript.exe adsutil.vbs set W3SVC/AppPools/Enable32BitAppOnWin64 "true"
Press ENTER.
To register the ASP.NET application
Open a command prompt and navigate to the directory
that contains the ASP.NET executable. For example, type
cd WINDOWS\Microsoft.NET\Framework\v2.0.50727
Type the following, then press ENTER:
aspnet_regiis.exe -i
For more information about the ASP.NET IIS Registration Tool (aspnet_regiis.exe), refer to http://msdn2.microsoft.com/en-us/library/k6h9cz8h(VS.80).aspx
Start the World Wide Web Publishing Service
Click Start > Run. The Run dialog box appears.
Type services.msc, then press ENTER. The Services dialog box appears.
In the list of services, right-click World Wide Web Publishing Service, then click Start (or Restart).