JRT, for BoB2, try dialling every possible option including resolution to the lowest value you can get (well, 640x480 or something) and see if it will start then. Important items are horizon distance, particle density, object quality, texture quality etc. If it can start on lowest settings you can then explore bumping things up. However, I fear that 64MB is just too low a value for the vidcard. The recommended minimum is 128, and it may be that the base textures will already overflow that - all the planes, for instance, are made in much higher resolution than BoB1.