I was 16. It was my first job. A summer internship in Lagos, Nigeria.
I remember cobbling together an account reconciliation macro in Excel (it ran as the default shell for Windows 2.0) on one of the IBM PS/2s and blowing the collective minds of the management (they were used to lotus 123 and had been trying for a unsuccessfully few weeks to reconcile accounts).
Much later, I learned to change the default shell to MSDOS Executive (Program Manager came with 3.0!)