Due to the heavy load placed on the CPU TRENDnet does not recommend running CPU usage over 70%.
With the following computer specs we would recommend no more than 6 cameras.
Intel Core Duo 2.5GHz, 2GB Memory, Nvidia GeForce 7100 256MB, 640 x 320 VGA view
With higher system specs you can run more cameras. Check the CPU usage while recording to ensure the CPU usage is not consistently over 70%.