Unable to figure out how to make a ISO image for a bootable CD

I'm trying to make a bootable CD from O/S files in a folder on my HDD. This is a 'Lite' version of XP Corp.
I use Nero V6.6 and for the life of me I can't figure out how to make a iso file to burn to a CD.

I did this before (a few years ago) but can't figure it out. A couple other programs allow making a iso file from a CD, but not from files on a HDD.

In Nero, choose CD, CD Rom Boot... You will need a bootable cd for Nero to copy the boot files from... Also have your folder ready to add to the compilation.

At least thats the way I remember doing it... Im old(er) now