Audio Interface With No External MIDI/Instruments?

i always enter midi data through the piano roll view.  i never use an external midi device or instrument.
 
i am getting a system freeze with a large project.  i currently have creative sound audigy se, and tried its WDM drivers, and also ASIO4ALL.
 
i'm confused on what type of audio device to get if i never plug an external instrument into it.
 
i have a quad core, 3.4 GHz CPU with 8GB RAM.   neither the ram nor the cpu get near their max capacities.
 
thanks.