Was my dream machine just a dream?

Well, there goes my entire plan.

I was going to buy a new computer so I could perform calculations faster, but I've decided against it now. After all, what guarantee do I have that electricity and semiconductivity will continue to behave the same way they always have? What guarantee do I have that I'll get the same answer if I perform the same calculation twice? For that manner, would my new computer even exist as a material object? Would Apple Computer be cheating me out of my money by selling me something that's not real?

These questions are tough -- I think I'm going to stop performing meaningful work and become a philosophy major instead.