I used MultiBootISOs.exe (now replaced by YUMI.exe) to create a diagnostic FAT32 USB boot stick for my Vista32 system and everything works perfectly. I like that it allows me to add my own ISOs instead of choosing from a set of preset ISOs.
The only "system" files in the USB root are:
1.) Boot (hidden folder):
-BCD (binary file)
-BCD.LOG (binary file)
The rest of the stick contains menu.lst and a bunch of diagnostic ISOs and folders referenced within menu.lst. I make changes simply by adding or subtracting ISOs and amending menu.lst as needed.
Are the 4 items listed above generic enough that they can be downloaded from the Internet and copied to my USB stick to make it bootable from scratch? Is it necessary to make the boot folder and ldlinux.sys hidden?
Finally, I'd like to know if my menu.lst would work for a 64-bit system as is, or if I'd have to change the hd32 references to hd64 to make it work. Thanks.
You did some excellent homework before heading over here, and you have most of it right.
The only things that you're missing are
1) There's likely a bit of some early bootloader code in the USB stick's MBR (first 512 bytes of the drive, usually hidden for the casual observer) so you'd likely need to grab the non-partition tables parts of the MBR (the first 446 bytes) and put them into the drive you wish to use to create a boot usb drive (ref)
2) The menu.lst entries are to tell grub how to find various bits of code referenced in each entry. It seems like, for some reason, it was under the impression that this usb drive was the 33rd disk on your system... and doing a bit of research it seems that's the way grub4dos works, as far as virtual optical drives are concerned. So, no, it has nothing to do with bit-ed-ness
Thanks for your prompt and informative response bmouring. I was hopiing things would be easier but your step 1 info makes the homemade option too fiddly for me. I'll stick with using 3rd party apps to create the initial boot USB.