RAID-0. which is supported on most modern mainboards, will almost double the transfer rate, but it will not help with access time. Which means that reading/writing large chunks will be significantly faster than on a single drive.

Alas, swap file use is not in large chunks. 4 K per swap. But there's a lot of transactions per second. If you want a fast swapfile, you don't need RAID-0,  you'll need a drive with a very fast access time. For now, the fastest access times on desktop computers are delivered by the 10,000 RPM Western Digital Raptor disks - and those are EXPENSIVE!
But they DO speed up Windows quite a bit. I can tell from personal experience.

Another thing: Poser does not access the drive very much during rendering, only when loading the objects and textures. During the render itself, it's all CPU based plus memory access. I tend to monitor memory size, CPU activity, virtual memory usage and page faults when doing a heavy Poser render, and I found that there are only a couple of swap file/disk accesses per second (if you have enough RAM). 

If you want to speed up Poser renders, install more RAM. More than 2 GB is only useful for Poser 7, which can use up to 3 GB of address space (and thus RAM) on Windows XP Pro, or 4 GB on Windows XP 64 bit.

In short, if you have 1.5 GB of RAM or more, disk speed does not affect render speed.

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

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