IIS 7.5 - Failed to Execute URL with a VC++ 6.0 dll

Hi All,

We have an working 32 bit ASP.NET application in 1.1 framework on IIS6 on windows 2003 server. In this web app, there is a page which calls a VC++ 6.0 dll using javascript and giving the dll with some parameters. This dll has a user interface which opens up once invoked. 

Now we have migrated the application to ASP.Net 2.0 (3.5 framework) and deployed it on Windows 2008 R2 having IIS7.5. We are running this application in 32 bit app pool (2.0 framework) running in Classic mode. Also we have configured the handler aspnet_isapi for *.dll having Execute permissions for this applicaiton. The VC++ dll has not changed in this whole process

Now when this dll is invoked we get the following exception

HttpException (0x80004005): Failed to Execute URL.]
   System.Web.Hosting.ISAPIWorkerRequestInProcForIIS6.BeginExecuteUrl(String url, String method, String childHeaders, Boolean sendHeaders, Boolean addUserIndo, IntPtr token, String name, String authType, Byte[] entity, AsyncCallback cb, Object state) +3234256
   System.Web.HttpResponse.BeginExecuteUrlForEntireResponse(String pathOverride, NameValueCollection requestHeaders, AsyncCallback cb, Object state) +393
   System.Web.DefaultHttpHandler.BeginProcessRequest(HttpContext context, AsyncCallback callback, Object state) +220
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8699714
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

We have tried running it in integrated mode, without isapi handler mapping etc but none seems to work. 

Any help will be appreciated

Regards

Piyush