WPyogi on "Problems with re-installing wordpress"

You can change the URL settings back in a number of ways without admin access - the functions file method is easiest IMHO -

http://codex.wordpress.org/Changing_The_Site_URL

You might also want to review:

http://codex.wordpress.org/Moving_WordPress

If you still want to delete everything, ask your hosts for help with the database issue.