Windows Vista is a system resource hog. There is little doubt as to that. But to go from there to Windows
Vista actually eating up RAM... Well, in fact you shouldn't blame Windows Vista for missing RAM in a certain
scenario. The scenario I am talking about is a 32-bit configuration with 4 GB of RAM. The system information accessed from Windows Vista will never show the whole 4 GB. Why? Like I said, it's not Windows Vista's fault. The fact of the matter is that you won't be able to see the whole 4 GB with any operating system.

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Microsoft, Windows Vista, 32-bit, Article