On two of my finals, my computer gave me the "blue screen of death." I was lucky in two ways. Firstly, when the computer restarted, it opened into ExamSoft giving me an option to continue my final. Secondly, the two finals that the computer crashed, I wasn't under a time crunch because I was blazing through the tests (I lost probably about 5 minutes each time).
I think the only option is to write your exam in that situation. Moving to a computer lab would be problematic because the software would have to be installed, you would have to be able login to your ID, and they would need an extra proctor.
My school's policy is to take a blue book and start writing.