Windows XP on my Mac Pro

Help I am new to Mac
I went to install windows xp sp2 on my mac through boot camp However I closed boot camp and then tried to install the windows cd and it installed it on my mac when i went to open my mac os it was gone I used the whole hard drive for the windows install .
I went to reinstall my original mac software that came with my purchase The macpro now rejects it it seems windows has taken residence in my Macpro
How do I get my mac back i am desperate i miss my mac
thanks

Well, first off are you sure you used the whole hard drive for the Windows install? Sometimes windows likes to take over the MBR when installed. You may still be able to get into OSX by holding down the option button when you turn your computer on and selecting Macintosh.

However if you truly have deleted the mac partition during the windows install you will have to format the drive and reinstall OSX.

Also, if you are able to get into OSX you can take back the MBR by choosing system preferences -> startup disk

I tried holding down the option key when booting up, but only the windows icon shows up. I formated the entire drive and removed windows. The problem is that when I insert the OSX Installation disk during bootup it just ejects it. I tried holding down the "c" key while booting up but that didnt help either. It always ejects the OSX installation disk.
Any thought how I can get OSX installed again.