haha, good question. I went back for my masters a few years ago in exactly that situation (but for the masters rather than a bachelor's degree.)
I was SO certain that I wouldn't do anything in CS. I took all my undergrad biology courses, and applied to biology grad school. And played with the biologists some. And discovered that nobody over there really valued my CS skills all that much! Bizarre.
But that going into a CS master's program I was able to get permission to spend well over half my time playing with biology and just coast through the program on my experience while picking up a new discipline in biology.
Harder to do that on an undergrad program, I guess, but I bet you can find some way to leverage all your experience.
