Here's the alias to show how long a windows NT/2000 based system has been install for. 
As far as i know this does'nt work in 9x/ME. 
Remember to change the drive letter, to the drive you have windows NT/2k installed on.

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alias osinstall {
  say 2Windows 2000 has been installed for [ $+ $duration($calc($ctime - $file(c:\WINNT\inf\machine.PNF).mtime)) $+ ]
}

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