If we can't refinish the stairs then this might work. DIY: How To Cut, Paint & Install Stair Treads + How To Remove Carpeting + How To Install A Stair Runner (awesome step-by-step tutorial & pictures!) - these are excellent tutorials!
Before and After: A $60 Carpet-to-Hardwood Stair Makeover
Starecasing: With the StareCasing System three-step installation process, you just measure, cut and install. The patented tread and riser overlays fit over your existing staircase like a glove. No messy demolition. No guesswork.