@K3nn3th,
to avoid editing iso files and booting them, You should avoid the Windows Boot Manager, which is my problem on one of my computers, and which I think is Your problem on Your current computer.
On my computer, a Quanmx KUBE-8080, I could boot 3 month ago the rootfsx.gz files of SliTaz 5.0 RC2 with both GRUB and GRUB4DOS. This was before I installed Windows 7, which I need for my job. Now this is impossible. I even get the same error on my display with SliTaz 5.0 rolling. I think it is because the computer boots first with the Windows Boot Manager, then it goes to GRUB or alternativly to GRUB4DOS, which I use to start SliTaz 4.0 and ISO files of SliTaz 5.0 rolling. I should have started booting with GRUB.
But there is an alternative. I can still boot the rootfsx.gz files of SliTaz rolling from my USB-Stick (/dev/sdc) on this computer. I have made it bootable with bootlace and had installed GRUB4DOS with the following commands.
X Term Terminal:
su
Password: root
bootlace --time-out=0 /dev/sdc
lzma d /usr/share/boot/grldr.lzma /media/disk/grldr
If You don't like booting from USB-Stick or CD or DVD, You should change to SliTaz 4.0 or should boot with GRUB or GRUB4DOS first of all. With only GRUB4DOS I had no problems booting rootfs.gz files on three different computers. But on a different hardware You can probably have different experiences.
Have You used the Windows Boot Manager?
Can You boot a SliTaz 5.0 rolling via GRUB4OS from Your USB-Stick?