Thanks hexbaz
Just to close it out, you should switch as there is a 1 in 3 chance of winning if you stick and a 2 in 3 chance of winning if you switch.
I think hexbaz got it first but silentc worked the hardest for it - so it's up to you guys for the next one.
In the meantime how about a discussion on the question I slipped in to the middle of the discussion. If a computer can't pick a random number, how can you pick a "truly" random number?