Trying to boot for installation

[George Reinhart]

I'm moving into Linux for the first time, though I was a Unix user in 
the 80s.  Downloaded the current stable version, and found that at 753MB 
it was too big to fit onto a 702MB CD.  So I looked back a bit and 
downloaded ubuntu-12.04.2-alternate-i386.iso, which fit, figuring I'd 
upgrade after it was installed.  This is going onto a Dell DHP, which is 
set to boot from CD but doesn't have the option of booting from USB.

So I start it up and it just repeatedly asks me if I want to retry the 
boot.  Is the .iso supposed to be a bootable file?  If not, what else to 
I need?  Will appreciate any help.

~GR