I would put them on the curb for recycling! You can grow a small plant in one, but the fuss and limitations are hardly worth the effort. But if you have your heart set on trying to grow in a PC tower, be ready to constantly trim, cutback, defoliate and cuss when they grow into the light. I did grow two plants using a PC tower as a "grow box", but it wasn't very productive for the time and effort expended.
Best of Buds
JB