suddenly gone

I am a Zen newbie and have installed the latest zen version. I also installed XAMPP so I could test the site locally. All was fine. I started to make template customisations, add pages, overides and suddenly all my pages are invisible. If i click on the home button I get a white screen and http://localhost/store/index.php?main_page=

Is there a master file that i have messed with by mistake?
Is there a test I can do to at least point me in the right direction.

Thanks

Did you make an over-ride for your new template?

If you did, can you login to your admin section and restore the default template?

thanks for the suggesion, tried it, no joy. browser bars says

"http://localhost/store/index.php?main_page="

and if I view the source code of the white page it is

anymore suggestions?? should i reinstall?

Thanks