Impersonating using SPUserToken object

using (SPSite site = new SPSite(siteURL))
{
   using (SPSite siteAsOtherUser = new SPSite(siteURL, site.RootWeb.AllUsers["WS2003\\Administrator"].UserToken))
   {
      SPWeb web = siteAsOtherUser.OpenWeb();
      //Write code with elevated privilege.
   }
}