Good morning (Ctr...) You could, of course install new stairs, however that would be quite expensive and I think there are some better options. However, I first need to know a couple of things. Are your current treads carpeted? If no, what is the kind of wood the treads are made of? Also what is the depth of the treads and how much do they overhang towards the front. This measurement will be at the sides where they are secured to the "stringer." The stringers are the sides that jog from step to step.
Thank you for this question and I'm confident we can solve the problem.
I've sent a message to your personal e-mail. Let's see if that gets to you and then I will offer some suggestions.
Okay Sandy I'm back with you... You can solve this problem with a low cost temporary fix or you can make a permanent change that will cost more. Both methods of fixing the problem are identical in the installation. The temporary (lowest cost) would be to use 3/8 ths inch plywood for new risers and stain them with a one coat stain/sealer combination. More costly, of course would be to use real oak and then do a more professional job of staining and finishing.
Thee ..... method.. A "cleat" of 3/4 inch by 3/4 inch and the width of a tread on the underside is cut. It's installed under a tread so it lines up with the back of the tread below it and back whatever thickness of wood will be the riser. It is glued and screwed into the bottom of a tread. The riser will screw from the back to the lower tread and from the front just under the tread above. This approach will maintain your current tread depth and you shouldn't be less than what you have right now. The screws going in from the front side should be countersunk so the screw head is below the surface. These are then covered with colored wood filler. Just repeat this process for each riser.
Tip : Regardless of which wood you choose, after the pieces are cut to size, you should give them all a first coat of stain. This will make the final finishing so much easier.
This should do it for you, but in case you have additional questions do not select the "accept" button at this point. Once you do that you'd have to go back through the whole process again to continue asking questions. Except, now that we have exchange e-mail addresses you can always contact me via that address.
Thank you for an excellent question, Dennis (cut2it)