There is no persistent storage on the raspberry pi AFAIK.
The configurations are stored on the SD card. So installing a new image on your SD card should work.
Yes, I agree with Paul, as you are not actually putting any software onto the Raspberry Pi itself, but as he says everything is copied onto the micro sd card, and when that is removed your Pi is in effect in the same state it was when you received it, or when it left the factory.
Once you have got things how you want them, it is often a good idea to remove that particular card, and to use a different one for experimenting, or trying out new ideas, other OS's etc.