Since scare tactics appear to be what compels some people to take secure your wordpress site a bit more seriously, or at least start considering the issue, allow me to shoot a scare tactics your way.
Everything you've worked for will go with this should your website's server return. You will make no sales, get signups or no visitors to your site, and in short, you're out of business until you have the site back up again.
Before you can delete the default admin account, you first need to create a user. To do this go to your WordPress Dashboard and click on User -> Create New User. Then enter all the information you will need to enter.
You can make a firewall that blocks hackers. The firewall prevents the hacker from coming to your files. more You also have to have updated version of Apache. Upgrade your PHP as well. It's important that your system is always filled with upgrades.
But realize that security is. Don't only be the reactive type, consider steps to start today protecting yourself. Do not let Joe the Hacker make your life miserable and turn everything in YOURURL.com creating come crashing down in a matter of moments that you've worked so hard.