Deleting an installation and re-installing C5 to start over is pretty straightforward but, if your site is fairly new, it may be easiest to go to Versions on the basic pages you wish to keep and restore them back to Version 1 (just delete pages you won't use going forward).
I have a video blog that can walk you through using versions at http://blog.arvixe.com/versions-and-concrete5-pages/...
EDIT (broken link) this video can be viewed athttp://www.arvixe.tv/video/A39SH17WH2NN/Utilizing-concrete5-Page-Ve...

Hope this helps

Adrian
Arvixe Web Hosting / Concrete5 Community Liaison |
http://www.arvixe.com/concrete5_hosting...................