I'd get a lift of Darrin in his Tardis (once he's finished rebuilding it) and go forward into the future first and steal all the plans idea's & technology from all those great things that are around in the future like the Natami, MiniMig AGA, X1000, Aros, MorphOS etc...
Battlle a few Daleks & Cybermen (who run Apple & Microsoft) along the way, then head back in time not to 1985 but to 1975 find the young Jay Miner and give him all the stuff. Then when 1985 came around he'd had developed & invented a machine the was so far ahead of it's time (even further than the original Amiga was) that no-one could ever beat it and he'd never have had to went to Commodore in the first place...
Thus in the world today as we know it everyone would be using an Hi-Toro Amiga and we could all live happily ever after...
