Use the i686...you will like it..maybe, if it installs good and recognizes your hardware.
I am running an install of F8 right now on interior hard drive , as well as having a F9 install on an external hard drive, that both came from Live Cd installs.
They are both i386/i686 type installs on a AMD64 X2 lappie.
So grab the i686...burn it..boot it.
The Live Cd won't "run" worth a hoot on an old x386 processor..it's to slow..so are x486 (i486) except for possibly a lightweight no GUI server (same for old beater i386's although very questionable). Better are at least PII's and up...but they install fine with the i386 cd's.
As long as you don;t try a x64 bit install cd on a P4 or AMD 32 bit processor, it should work. (if the hardware is recognized well)
Go for it!