Retrieving the COM class factory for component with CLSID Error: 8000401a

from last so many times I am getting the below error.As I am using the Microsoft Word dlls to create word files which further attached to the mail.

Server Error in '/' Application.
Retrieving the COM class factory for component with CLSID {000209FF-0000-0000-C000-000000000046} failed due to the following error: 8000401a.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Runtime.InteropServices.COMException: Retrieving the COM class factory for component with CLSID {000209FF-0000-0000-C000-000000000046} failed due to the following error: 8000401a.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[COMException (0x8000401a): Retrieving the COM class factory for component with CLSID {000209FF-0000-0000-C000-000000000046} failed due to the following error: 8000401a.]
   iPortal.user.sendRAMail.GetData(Object fileName) in XXX:512
   iPortal.user.sendRAMail.btnSend_Click(Object sender, EventArgs e) in XXX:1300
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +107
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +110
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3436


Version Information: Microsoft .NET Framework Version:2.0.50727.4216; ASP.NET Version:2.0.50727.4223 

can anybody please suggest me any solution.As I am also got some solutions that say me to change the access permission for the Word dlls using the DCOMCNFG but still getting the same error.but on some time it works properly...so I think the code is not an issue. And also how I will find which account is using my current application.(ex.Network Service, Administrator etc)

I found the solution,

using DCOMCNFG.exe open it and go to Component Service ->Computers->My Computer->DCOM Config-> check for Microsoft Office Word option and select tab Security.Here you will get the options for Launch and Activation Permission->select Customize and click on edit and the add the user that will runs your Application with full access.

That's all ,this resolve my problem hop this will help.