Computer towers are typically housed in high impact, hard plastic cases or Bakelite, or metal panels and cases; some towers incorporate both materials. These components will need frequent dusting. Consider buying plastic or fabric covers for computer equipment operated in a dusty environment.
Twice a year, vacuum the ventilation slots on the case, particularly at the cooling fan, to suck out accumulated dust and debris. Turn off the computer, but don't unplug it. This helps maintain a good electrical ground that helps guard against damage from static electricity. Gently vacuum the interior of the case to remove dust buildup on circuit boards and panels.
Never pour or spray any cleaning fluid onto any electronic device – doing so increases shock hazards, and it's the quick way to ruin the equipment permanently. Avoid using abrasives to clean any plastic or painted surface. They will scratch the surface and make future cleaning more difficult.