Missing Iphoto

I have just re-formated my hard drive on my new MacBook Pro 15inch. I re-installed the two discs that came with it, but to my confusion my "Iphoto" is missing!?. I looked through the discs that came with the computer, and it seems they do not have iphoto. I find this all rather bizarre if Apple have decided to pre-install that software with out a back up disc to re-install it again. they seem to have great faith in there computers for not going wrong and in need to be ever re-formated...I always re-format my hardrive on laptops every month or two ( to keep my computer in top working condition ).., maybe it's just a windows thing before i turned over to Mac this year lol. How do I get my iphoto back?. Can I re-download it?, giving out my mac id number?...or maybe i can walk in to the shop where i got the computer from (a Mac store) and they can re-install it again?.

Many thanks for anyones help in this matter

Thanks for your quick response . What package would it be in, there is a lot of packages, but none say iphoto?! .
My mac is working on a Leopard operating system.

I have re-installed the 2 discs, and there was NO iphoto to be seen?!, unless it is in a package that is under a different name?.