asp 3.5 Update Problems

We are in our programming Office decided to update our Software tools and upgrade it
from ASP.Net 2 to ASP 3.5 ,I mean from visual studio 2005 to VS2008 ,the every thing
is done well , thank God , But there is an issue which cause me head pain, At certain
aspx page which not shown at design mode properly and gave the error message on the
Script Manager Ajax Control which is "Error Creating Control - ScriptManager1The server tag 'asp:ScriptManager' is ambiguous. Please modify the associated registration that is causing ambiguity and pick a new tag prefix."
after i turned around searching with google i found some talking on WEB.Config file
So i checked this line which is Correct in my page
"
"
the error at some when the version is older

But at my case i found in my aspx page the line which cause my problem which is

"<%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
Namespace="System.Web.UI" TagPrefix="asp" %>
"
that's happen Because conflict between 2 different versions of Ajax ToolKit 1 and 3.5 the solution smoothly
Delete this line of code ,So conflict solved and ASPX page appears Perfectly at design Mode Perfectly

Hello , For all people who interest in Dot Net Programming and Oracle and sql DB
that's my first ,I decide to Blog my experiance to help every one who face some difficulty as me in some programming issues ,I think that's important for me to remember every problem i faced and remember it at the future, over all I think that's my role in the life is to help other people as there are other helped me on the past , Also i think that's necessary to take a knowledge from Each Other to develop our world