what do I have to do to start linux from an ISO?

Welcome to LQ
Burn the iso to a CD, and boot the computer from CD
Or use a virtual machine in windows, like qemu,

Hi,

Welcome to LQ!

If the 'ISO' is an image then you must use a application on a machine to create a image on a CD/DVD if that is the media of choice.

Some distributions have a 'USB' install methodology so I suggest that you look at the distribution's web site for a 'HOWTO'.

With the media of choice you would have to setup the machine to boot from that same media; either 'USB' or 'CD/DVD'.

Just a few links to aid you;

Linux Documentation Project
Rute Tutorial & Exposition
Linux Command Guide
Utimate Linux Newbie Guide
LinuxSelfHelp
Getting Started with Linux
Advanced Bash-Scripting Guide
Virtualiation- Top 10

The above links and others can be found at 'Slackware-Links'. More than just Slackware® links!

Also tell us the name of the ISO, so that we understand which distro it is [provided you didn't rename the ISO], it will help us guiding you with further details.

Post the complete name of that iso file.
Check
If it is matched then burn it to cd/dvd.

Are you talking about starting up the entire system from the CD, or are you just trying to install it to the disk?

An ISO is a disk image that needs to be burned to a disk in order to work properly. Since you are on Windows, a program such as Windows Media Player, Infrarecorder, or Nero may be used.

After that you will need to make sure your computer can boot from the CD. This option will be in your computers BIOS. To access the BIOS, you press F1 or ESC, depending on your BIOS. From there, you can edit your boot order to boot the "livecd".

If you want the whole system to start, then you need what's called a "live cd." Your particular ISO may or may not have this ability, so try some searching online. I know Ubuntu has one because I have used it before I also think Fedora has one as well. It will most likely be listed as an option once you start up the CD, so just click that.

Welcome to LQ, and hope I helped. Enjoy Linux.

Just make sure you're using the "raw image" option when writing your ISO to CD. (in the drop down list, make sure .iso is there).

A great image burner that I have used in the past is IMgBurn.