If it helps I run BA on a laptop which has a core 2 duo centrino (T5550) processor with 3GB ram. Using Vista home premium (32 bit) with office 2007.
I also run it on a quad core desktop and I find even a cranky large excel spreadsheet runs fine, and still allows other processes to continue uninterupted.
However I only use a 1 second refresh and so perhaps if you wish to trade and have uber fast code then an uber fast pc with big ram and high bandwidth could give you a nice feeling of being as fast as anyone else in the trading room
