It'll show them the info about your servers Hard drive... And as far as I know, there's no way to show their hard drives info... But, just in case you want it for some other reason, try the vol command in WinXP. atm, I don't have time to work out a script to just get the serial number. But, the output is as follows (on my machine at least):

Volume in drive C has no label.
Volume Serial Number is 7C9B-238A
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