How can virtual machines consume so little RAM on the physical host machine?

"The columns in Task Manager can give misleading figures -- for accurate memory usage per process, you could use perfmon (Performance Monitor in Control Panel) and look at the ""private bytes"" figures.

To show this, go into perfmon, click to add the counter (I'm a Ctrl+I kind of person). The ""Performance object"" would be ""Process"", with ""Private bytes"" being in the counters list -- obviously you'd need to select the relevant process from the right hand list."

"It could be virtual memory, memory-mapped files, or something similar.

Have you tried displaying other columns in Task Manager?"