well it depends. Kontakt 3.5 has a very very light print on RAM thanks to it's brand new streaming technology. I mean instruments that used to take 120+ megs now take like 67mb. With one gig of RAM you can expect to hit brichwalls regarding how many instruments you can use rather quickly, but it is not impossible.
Instruments to stay away from. All the KS (KeySwitch), if you load instruments that only have one articulation, they take up about 6-12mb each.
But Absynth, Reaktor 5 and Battery 3 may not like your CPU. Those can get quite intense, especially Absynth, it runs slow on my computer just opening it.
Buy a second stick or RAM for sure next since it's the cheapest upgrade next to buying a new PC. Be sure that your RAM is at least DDR2 800mhz. They should both be this speed, if one is 667mhz and the other is 800, the computer will dock the faster one down to 667 to match the slowest. Also with 800mhz you could always transfer those to another computer when you get one, longer life cycle.
danicos
No, no i dont think so