pues prueba esto
hipervinculo=""& request("menu") & "/" & request.QueryString("letra") &"/"
hipervinculo=replace(hipervinculo,"&","%26amp") '<-----------------------
Response.Write "<a title="" (" & tama & " Kb.) "" href="" clicks1.asp?url="&hipervinculo
Response.Write file.Name & """ onclick=""parent.cambiar(this.href);return false"">"
Response.Write palabra
Response.Write "</a>