The formation of two-component multilayer films on solid surfaces is studied using the Monte Carlo simulation method. The properties of systems exhibiting negative deviations from ideal mixing are discussed. Phase diagrams for systems undergoing layering transitions are determined and compared with the results obtained for systems exhibiting ideal mixing. Also, the problem of wetting and prewetting transitions in mixed systems is considered. It is shown that the presence of a preadsorbed layer of one component influences considerably the wetting behaviour of the second component. In particular we have found indications that under certain conditions the systems exhibit prewetting transition.