You can size, locate, and play as many videos at once as your system resources will handle. DirectRT pre-cues them before each trial begins so synching them with precise onset times (relative to each other or with other stimuli/RTs is easy. They are all played through the DirectX DirectShow/WMP video engine so most video formats are compatible.

See also:

www.empirisoft.com/directrt/help/html/directrt_stim.htm

Let me know if you would like a hand with putting together a particular task.

-Blair