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Download and run "SPECCY" - this will give you details of the computer and everything inside it; along with serial numbers.
Another good program is "Belarc Advisor" - this also will give you a wealth of information.
SPECCY does not show which model compaq presario 56 one has. It shows basically what's in your device manager. Don't waste your time, like I did. It still did not answer the topic being discussed.