Confused about 64-bit ISO

[Chris Henderson]

I have a x86 computer where I can install a 64-bit O.S. I need to
install a 64-bit Redhat AS or ES in there. But when I go to Redhat's
ISO download section it gets very confusing with various options. I
have downloaded and burned a 900MB Red Hat Application Server v. 2 (AS
v. 4 for x86_64) but can't seem to boot off the DVD. If it's a 64-bit
O.S. then why it's only 900MB and why can't I boot off of it? I'm not
sure what's Intel Itanium or IBM Power or Intel EM64T is.

Could anyone please point me to the right 64-bit ISO for x86?