This is what I have in the top of my page

<%@ Page Language="C#" AutoEventWireup="false" MaintainScrollPositionOnPostback="true"
	MasterPageFile="~/admin.master" CodeFile="Registration.aspx.cs" Trace="false" EnableEventValidation="false"
	Title="FC Admin - Registration" Theme="Profesional" Inherits="Registration_Form" %>
<%@ Register assembly="skmControls2" namespace="skmControls2" tagprefix="cc1" %>

<%--<%@ Register Src="../../UCD/Tags.ascx" TagName="Tags" TagPrefix="uc5" %>
<%@ Register Src="../../UCD/AtHomeManMatch.ascx" TagName="AtHomeManMatch" TagPrefix="uc4" %>
<%@ Register Src="../../UCD/FriendsAvailbility.ascx" TagName="FriendsAvailbility"
    TagPrefix="uc3" %>
<%@ Register Src="../../UCD/VFriendsAtHAvailbility.ascx" TagName="VFriendsAtHAvailbility"
    TagPrefix="uc2" %>--%>
<%@ Register Assembly="SqlWhereBuilder" Namespace="UNLV.IAP.WebControls" TagPrefix="cc2" %>
<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="ajax" %>

Why I'm getting
Error 102 The type 'System.Web.UI.ScriptManager' exists in both 'c:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions\3.5.0.0__31bf3856ad364e35\System.Web.Extensions.dll' and 'c:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions\1.0.61025.0__31bf3856ad364e35\System.Web.Extensions.dll' C:\Development\Visual Studio Projects\WebSites\FCAdmin\Coordinator\People\Registration.aspx 1 1 C:\...\FCAdmin\

Do you know how can I remedy this problem?

>>Hi everybody,
>>
>>I've downloaded a great class from the http://aspnet.4guysfromrolla.com/articles/020608-1.aspx#postadlink and was able to add one custom method to it.
>>
>>So far, so good.
>>
>>Now, I want to be able to use this class in our project. Is it possible without having a separate project for this class? Would you please guide me on adding this class to the existing project and including it on the Toolbox?
>>
>
>Yes, just add the *.cs files to your project. Copy over the *.gif and *.js files as well (I normally have a folder for my images and another one for my JS files). I think the other thread answers how to add them to the toolbox.