More often than not, swapfile churn is caused by the virtual memory being set too HIGH, not too low. The default windows settings (especially in XP) tend to force everything through the swap file, when I reality it would be better to allow direct memory access.
Tis usually best to change the swap file settings to "auto / allow windows to manage...."
The problem with setting it too high is that everything gets forced through it, even at low workloads, slowing the machine