just attempted to 3 box on my setup.

C2D E6400 (barely pushing 60% at full load load 10% idle w/ all 3 running and ventrilo and firefox)

1gig Dual Channel DDR2 RAM (95%, was 75% w/ 1 copy running)

ATI Radeon X1300 PRO (nothing to monitor this)

Im constantly monitoring my system atm via G15 keyboard screen and temp gauge on my box. Currently running at a fairly cool 85F (~30C)

Using default gfx settings, no mods to save ram.

Its running pretty smooth, the only lag comes when one of the accounts is logging in (of course)

I must say i'm pretty impressed w/ the performance considering my pc is far from top end, but running 3 copy's fairly easily. Maybe im just lucky?

Now i need to learn to control all 3 windows at once >.<

PS: I honestly think that an extra stick of ram would make things run even smoother, tho as i said, its running pretty ok atm.