Someone Hacked my user/pass code

My username and/or password no longer work. I run Advanced Guestbook 2.3.1.

I've always had spamming problems, but now, out of the blue, I can no longer access admin control.

I am not familiar with HTML coding and such. I have a webmaster who doesn't know what to do either.

Is there an alternate "master code"? What do you guys recommend.

My site where the guestbook is posted is www.kentkoller.com/guestbook

THANK YOU FOR YOUR TIME.

Sorry if this is one of the things covered in the "READ THIS BEFORE YOU POST AN ENTRY" section, but I'm rather ignorant when it comes the vocabulary you guys are using in that section.

Yes because the English I used here is so damn complicated

Resetting the Admin Password:

With Carbonize's reset.php file:
http://proxy2.de/forum/viewtopic.php?t=4071

Well I'm glad you can admit that you are way more knowledgable on computers than me, especially in such a nice, thoughtful manner.