I've maxed out all of the equipment. I've got the $500,000 version of everything. Trust me, that's not too difficult to do once you're mining in the 3,000-5,000 ft. depth. It's a shame cos it's not nearly as fun once everything's been purchased. They also sell the game on CD for $15, btw. I wonder if it would run full-screen then.
I wish they'd make a Pocket PC version. That'd be badass. They'd probably have to program it from scratch, though. That game seems to have similar resource requirements to games like Far-Cry. Check out your Processor Performance in the Task Manager while you play. I've got an Athlon 64 3200 with 512 MB of RAM at work and it pegs a consistent 80% usage when the game's running.