Cannot use program, not supported by architecture? I have a MacBook running 10.5 and have a Snow Leopard upgrade disk to 10.6.3, and that is the error message that I keep getting as to why my update won't install.

I have a MacBook that I am trying to upgrade to Snow Leopard so that I may upgrade it then to Lion to make better use of my iPad and some of the n we tools that Apple has made available in Lion. I have checked and double checked that my MacBook meets the hardware expectations, and it does exceed the ones for Snow Leopard. however, every time that I try to run the install disk it tells me that the program is not supported by the current architecture. I have even tried to backend the processes by opening the install folder with "View Package Contents" option, but it still gives the same error message! Someone please help!