Acctually, RAM does it all. Mordin has, indeed, a very nice computer except for his terrible low amount of RAM.
I have an Intel Pentium 4, 1400 mhz and 128 mb RAM, and the game still lags after 2-3 hours of gameplay.
RAM is very cheap right now. Buying another 128 mb cost only what BG2 itself cost. I would recomend you to get som of that.
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We call him Bobby Corwen