you computer is x86
so i guess you download the x86_64 images...
if you are new to linux, you should try ubuntu
http://www.ubuntulinux.org/
that's the linux version i use... I tried fedora, but found ubuntu to be a lot easier...
edit:
correct me if I'm wrong...,
... x86 is 32-bit computers... x64 is 64-bit computers....
I'm not sure about i386, although it sounds familiar... and i think ppc is for macintosh...