Boot from External CD Drive (ISO file)

[Donn]

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.

[patio]

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.

[Donn]

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 there

[patio]

Whats on the CD and how did you build it ? ?...it makes a difference...

[Salmon Trout]

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.

[Computer_Commando]

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.htm

[patio]

Kinda where i was goin with that...