If it's a new installation (and assuming you didn't set up a database), you should be able to copy over the App_Data directory from the install and stop/start the website.

You'll have to re-create the account, but at least you'll have a good admin account to do it with.

If you've already made modifications and don't want to start over again, you can parse through the App_Data directory for user account information. Replacing appropriate files should do the trick for you.