Well I'd probably try and commit suicide at one point or another, and after realising that I'm immortal I would stop bothering to gather supplies to keep myself alive as my body can't degenerate or anything. I'd read up on all my school textbooks and then from that study further of physics and electricity from universities until I can build generators and use those to create power.
Seeing as I have infinity time, I'd further my understanding in almost everything around me, and then because I can't die I can explore inside volcanoes (ie. in lava), dig underground and expand on the scientific knowledge that the human race already had. With knowledge in carpentry and building I'd build a house (as by this stage all current buildings are probably all delapidated after four hundred years of being uninhabited), figure out how to run vehicles and drive insanely fast for fun. Learn how to fly and eventually get to mining, producing aluminium and sulfuric acid and all chemicals needed. I'd figure out ways to get all these things to run automatically, or at least with little human interference, learn robotics and develop that technology until I can get things automated enough to work as they would if the human race was alive in 2010 (even though by this stage it would probably be in the 3000s by the time I've built all of these factories and mines single-handedly). After this, create supercomputers to store information with artificial intelligence (I'm immortal, what do I have to worry about AI taking over?) that can invent better than the human mind, and find ways to use wormholes, to harness gravity and to travel to other planets, make them habitable, spread animals to different planets, make some planets purely industrial and make a single-man empire. Oh yeah, and at some point I'd try and recreate human life, but it'd be hard to do without having living humans to test things on (for example creating an artificial womb with no live model to base betas on would be hell).
Oh yeah, obviously I'd do some fun stuff as well, like once I restore power, create and record a wide range of songs, become perfect at drumming, guitar, bass, keys, violin, clarinet, trumpet etc. But yeah, needless to say, all this would be a sad existance, all triumphs would occur over such large periods of time that you'd hardly feel successful at all.
Probably hang out with some dogs
And of course this.
