Mac partition deleted? Pls help.

Hi, thanks for reading. I just bought a new macbook last night, and I wanted to install a Windows XP on my macbook.
But now i'm sure that i've accidentally replaced my mac partition with the windows XP, and the windows XP hasn't finished installing.
Then I tried to restore my mac and install the Mac OS all over again, but it doesn't work.
I booted the Mac OS X CD that came in the box. When I reached the point where it asks where to install the OS, it was blank and I couldn't continue. I read somewhere that on the bottom left corner there was an "options" button and we can "erase and install", however the "options" key could not be pressed.
I also tried going to disk utility, but all the options for erasing and partitioning could not be pressed. And right now I have no clue what to do, as all that's left in my mac is a half installed Windows that doesn't work.

Anyone have any suggestions? All I want to do is just restore my mac like new if thats possible..
Please help, it would be greatly appreciated (the macbook is my birthday present from my parents and my birthday is tomorrow!! It would be a shame to disappoint them if they find out that I destroyed their present!)

Thanks again!

Boot the MacBook with your Leopard installation DVD 1. Cancel your way out of the install process and select Disk Utility from the top menu.

Select the hard drive (highlight it) and then do an erase. Once that completes (should be fast) select the hard drive again and format it as one partition using the HFS+ format. You should also name the hard drive in this same step. Name the hard drive "Macintosh HD" (without the quotes).

After that completes, install OS X and all its applications.

Before attempting to create a Boot Camp partition again, be sure to read and understand the instructions as given in the Boot Camp Installation & Setup Guide.pdf.

Regards.

Thanks a lot chscag! Your advice really helped. It's working just fine now.