Well, for one I just came across WMI today as a possibility while searching for info on finding SCSI serial numbers, and haven't found a clear example yet on how to do it that way. The example I found for VB doesn't work:
  set objinst = GetObject("WinMgmts::Win32_LogicalDisk='C:'")
  MsgBox (GetObject "WinMgmts::Win32_LogicalDisk='C:'").VolumeSerialNumber)
VB didn't like it. Changed the second line to:
  MsgBox objinst.VolumeSerialNumber
But the first line gives me an Automation Error, 0x80041012.

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And two, I don't want to have to install WMI on 95/98/NT4 just to get at this one serial number, even if I do figure out how to get WMI to work.