A B757-200's two Air Data Computers and TAT probe failed after takeoff. The flight returned to land.

Narrative

We had just lifted off the ground; when we got a 'TAT Probe' EICAS message followed immediately with an AUTO THR DISCONNECT message. At 800 FT AGL; I asked for 'Flaps 1; VNAV' and only got VNAV armed; but not engaged. That made sense because of no autothrottle. So I manually set the thrust to accomplish what I needed. Once we were cleared on course; I then asked for LNAV and again only got it armed; not engaged. We were cleared to 14;000 FT and given a frequency change over to Center. By now; my First Officer was in the book looking up 'TAT Probe'. The book said to avoid icing conditions if possible. We called Dispatch and through a three way conference call; talked to Maintenance as well. Maintenance had us try pulling and resetting breakers to attempt to restore TAT heat. As were trying to restore TAT heat; ATC was clearing us to higher altitudes with thick cloud layers way above us (icing conditions probable). We elected to stay in the clear at 14;000 FT temporarily while running the maintenance drills. After a bit; Maintenance finally told us that he couldn't suggest anything more. So with icing conditions before us and above us; and with no LNAV; VNAV; or autothrottles; I saw no reason to try and chance fate. We elected to return to get the problem looked at. We advised Dispatch of our decision and returned. Upon our return; maintenance did some diagnosing of the problem and found both Air Data Computers were faulty; as was the TAT probe itself.