Particle systems and hair are calculated by the processor and then the resulting geometry is handed off to graphics card to draw using OpenGL. That graphics card can handle a million or more particles in realtime (30+ FPS) so that’s probably not the bottleneck you’re experiencing. It sounds to me like the processor is the bottleneck at least regarding particle systems and hair. It could also be swapping to the disk if running out of memory, but that can’t happen anymore with 4GB on Windows XP because all of the addressable memory space is already physical memory.
When you’re working on something open up the task manager and watch the processor activity. You’ll likely see one or both processor cores maxed out when working with particle systems and hair. If you want to improve the performance of CPU bound tasks I’d suggest looking at upgrading the motherboard, processor, and memory. Spending $400 or $500 on those components could provide a substantial boost in performance over the Celeron processor in the system now.

) You don’t think I’d get any noticeable performance increase at all?