Thanks everyone for your replies. Looks like I need to get a better machine!

And that brings up the next question, along the lines of what jazzmammal was suggesting. It's apparent that the "minimum requirements" on the link posted by Matt Finley don't really cut it - perhaps they're the minimum if you want to play MIDI only? But if you really want to use BIAB 2013 with styles and RealTracks to its full abilities, what realistically is the minimum hardware and software needed? 32 or 64 bit? 2 GB RAM? Duo Core (whatever that is)? What exactly influences the geekbench score? I don't want to get another machine and discover it's not up to par, but I don't want to pay for way more than I need either.