On my levono thinkpad sl410 there are two vents. The laptop has two CPUs - does that mean that each fan has its own vents?
Your system does not have two physical CPUs. As you mention two CPUs, it's likely got a Core 2 Duo, which is a single piece of silicon that has two CPUs in it, aka a dual-core processor.
See Multi-core processor on Wikipedia for more details.
Most likely, both vents are connected to the same fan and are to optimize airflow (maybe one flows in and the other flows out).