..while 86 percent of its Windows 7 machines are regularly consuming 90 percent to 95 percent of their available RAM.

Though SuperFetch is a little less aggressive in Windows 7, it will still use a substantial amount of memory—but with an important proviso. The OS will only use memory for cache when there is no other demand for that memory. If an application needs lots of memory then Windows will discard cached data to make it available to the application. The rationale for this behavior is simple: memory that is currently not used by anything at all is memory that is wasted. Filling unused system memory with data from the disk just in case that data is useful is much better than leaving the memory unused. Why? Because if that data is needed—and SuperFetch strives to ensure that the data it loads is likely to be needed—having it already in memory means it can be used near-instantly, rather than having to wait tens of milliseconds to load it from disk.

Windows XP, with its "low" memory usage, does nothing like this, thereby "boasting" much higher free memory figures. But as should be obvious, such figures are nothing to boast about. Windows XP just allows a large proportion of system memory to go to waste.

So it was little surprise that, upon checking my reported stats on XPnet, I found that I too was in the "alarming" position of having virtually no free memory. A quick glance at Task Manager revealed the truth. Though my "free" memory is indeed negligible, this is because so much is used by cache. The important number is not "free," but "available." The "available" memory includes both memory that is free, and memory that can be trivially made available, and this figure is far more representative of the true amount of memory available to applications. The vast majority of cached memory can be freed up near-instantly, since it is used up merely by cached data from disk.