USB Boot Errors
Linux has its own set of popular error that it throws at those brave enough to tinker with its internals.
No active partition
No bootable disks found. Insert a bootable floopy and press any key to continue
In this case, you probably have no active partition on your supposedly bootable disk. Even if your MBR and partition boot code are fine, Intel BIOSes will blatantly refuse to boot if there is no active partition.
Syslinux gives you “Boot error”
“boot error” is what the Syslinux first stage bootloader says when it can’t read the second stage for whatever reason. Sometimes it’s the BIOS not handing sectors back correctly (even some newish Award BIOSes still get this wrong for USB sticks) and the Zip disk workaround will generally fix this. Sometimes it’s because the syslinux command that builds the list of blocks to load had a different idea about the BIOS device numbering than the BIOS does. Sometimes it was because I’d forgotten to re-do the syslinux command, and had done something to the USB stick that had moved the second stage file to different disk blocks; this one was a pain, since the boot loader kept working using a second-stage boot held in blocks marked free, and didn’t fail until those blocks happened to get overwritten by something else. It’s all a bit of a black art.
Try downloading the Trinity Rescue Kit, burning it to CD, booting it (let it run from CD, don’t make it run from RAM) and using trk2usb to make your pen drive boot it. TRK uses the zip disk workaround. Betcha it works. If it does, set your own Linux up the same way.
Renaming DOS/FAT Partition
sudo mlabel -i /dev/sdb ::`<new-label>
Note the double colon preceding the label.