I was have SMS 2003 client and I install SCCM 2007 sp2 and I push SCCM agent ,, but I found this error in some clients Failed to successfully complete HTTP request. (StatusCode at WinHttpQueryHeaders: 500) the agent is installed but it;s not approved ?? Amr Nassar

Have you already tried one of the numerous solutions mentioned in those articles: http://social.technet.microsoft.com/Search/en-US/?query=WinHttpQueryHeaders%20500&rq=meta:Search.MSForums.ForumID(3b2f8eba-27e4-41c9-bc61-7799a1507e9e)+site:microsoft.com&rn=Configuration+Manager+Setup%2fDeployment+Forum