I am trying to boot from a external CD DRIVE that is connected to my Toshiba labtop.

Problem: I am unable to boot the CD.

Details: When the external is connected to the labtop via USB 2.0, I get a black screen with a blinking underscore. (at most i waited 2 mins, got impatient so didnt fully wait to see if it would disappear) When it is then unplugged the black screen goes away and it becomes normal. Thus I am able to see the "press f2 for boot OPTIONS" press f12 for boot menu".

When I try at this point and connect the external cd drive to the labtop during the bios setup i get 3 options;
HDD, FDD and lan.That means it's an older LAPTOP that does not support BOOTING to a USB device.
What are you attempting to FIX on this PC ? ?...perhaps there's another method.What do you mean older labtop? My labtop is relatively "new" Toshiba T235

Also I waited out for 4 minutes w/ the disc in the external black screen w/ underscore still thereWhats on the CD and how did you build it ? ?...it makes a difference...The thread title includes "(ISO file)". If the OP has just burned that to a disk, so that a DIR shows blablabla.iso then it will not boot.
Thread title indicates ISO file was probably just copied to CD.
To OP: ISO files are actually images of complete CDs or DVDs compiled as one whole image file (*.iso), just like Ghost does for hard disks and partitions.
http://www.petri.co.il/how_to_write_iso_files_to_cd.htmKinda where i was goin with that...