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Recently my system has been rather sluggish. I have 4 GB of RAM, most of the time I don't have anything super heavy open (2 browsers with a significant amount of tabs, Java IDE, Skype etc.).
When I add the "Working set" column values in Process Explorer for the most memory-consuming processes, it doesn't even reach 2 GB. Despite this, Process Explorer tells me that 3.5 GB of physical memory is consumed.
How can I find out what's eating up my RAM?