Well this howto you're referring to strikes me as a very messy one.
Another thing I don't get: why use Windows and GRUB4DOS to accomplish things which are easier to accomplish using native linux utils and from Linux itself?? Especially when all the thing is about booting various Linux distros?
Finally, why not try to use GRUB2 to boot directly from the ISO
? That would take only 1 partition.This approach works fine for me to boot multiple distros without resorting to this highly suspectful configuration with multiple partitions on a USB drive, some of them even being logical discs...
OK, since you're set to stick to this idea, there is one thing you must try:
When you boot from the stick (after configuring your BIOS to boot from USB stick), you get into GRUB2 menu.
Good! Then you can press C to get into the GRUB prompt and from here you'll be able to actually see what can work and what can't.
So, in GRUB2 prompt you type `help`, which gives you the list of commands. You can print them out first from the online man page, though.
Then you have the `ls` command to list all available drives. OK, much better now!
Then you can `ls (hdX,Y)/` to see what's there on the drive. Just like searching the directory from BASH.
Thus you will be able to see which partitions are visible to your GRUB, and which (alas!) are not.
Once you make sure that ALL your partitions are visible to GRUB, that's a great relief.
Then try to issue your commands from your grub.cfg, but now from command line. You'll see which command fails. When you finally give your command `chainloader +1`(for example), GRUB will either swallow it, or give off error. If no error, the you type `boot` and see what happens. If it doesn't, then you'll have to spend I don't know how much time trying to figure out what is wrong with syslinux loader on the given partition...
then if nothing helps you can try the trick with installing syslinux into MBR and copying the bootsector into GRUB config folder and reinstall GRUB. It will point to the needed files on the partition to boot, given the partition is available to boot from.
But I must admit, the idea of booting from LOGICAL DISKS seems to be the most vulnerable point here. I never use logical disk even on HDD, let alone USB sticks, let alone making them bootable.