When you say "tinkering", do you mean he's been using his screwdriver under the hood, or just playing about with software settings, etc? Assuming the latter, check in the BIOS to see if the parallel port (LPT1) has been disabled. You didn't mention which operating system is being used, or the type of printer. Check the printer cable by substitution with a known good one. If you have an MS-DOS boo disk (say v6.2 or similar) with PRINT.EXE included on it, try booting with it and then printing a text file to LPT1. If this works, then it suggests your operating system needs to have LPT1 re-installed. If still no go, then try checking the parallel port with a loopback plug and something like CHECKIT.
ROGER - GØAOZ.