[syslinux] boot fails on some system

[Ady Ady]

> 
> "Missing operating system." 
> "Operating System not found" 
> 
> and keep still ...  I can reboot the computer with Ctrl + Alt + Del.


A simple search in the Syslinux wiki (or even a web search) would tell 
you that you are probably lacking the "boot" (aka "active") flag 
enabled on the adequate (primary) partition.

After trying that, I would suggest, based on comments you previously 
posted, for you to start by trying a simple one-and-only FAT partition, 
on a simple USB flash drive, using one (live) distro, and only one.

Using multiple partitions, with the possibility of multiple different 
distributions / tools while having enough compatibility with multiple 
different systems at the moment seems to be (much) further down the 
road. Moreover, there are auxiliary tools that can help 
less-knowledgeable users, instead of doing all the steps manually. If 
you have some Windows OS, there are even more auxiliary tools to choose 
from, and with them, many web sites / forums dedicated to the matter.

Additionally, I would suggest reading, a lot. Just a basic page would 
be the page about USB devices on the sysrescuecd site.

Regarding the system that is not booting, you might probably want to 
check whether it is a UEFI system.

Finally, please consider that the specific directories in which you 
install SYSLINUX and the location of specific files (and their 
versions) are also part of the troubleshooting process.

Regards,
Ady.