Yes I meant that XP had the problem, and that Win7 tried to remedy it.

You are overlooking that the read-only part of the working set can be released immediately once another process needs those pages -- just zero them and add them to the free list. Only the dirty pages need to get written out to disk.

Anyway, it would actually be simple to test the effectiveness of the working set cap by writing a program that allocs and dirties memory aggressively, and then running it either in normal low priority or background modes, to see how it affects overall system behavior when running in each mode.