Or is this a case of Win7 using the available/unused memory for caching kinda like what Linux does? And, if so, whose bright idea was it to tell the user that

Or is this a case of Win7 using the available/unused memory for caching kinda like what Linux does? And, if so, whose bright idea was it to tell the user that this memory was "unavailable" in the task manager? The whole thing is rather silly. "Operating system X prints this number, while totally different operating system Y prints a much bigger, possibly unrelated number! Everybody panic!"