I've got a relatively old PC (circa 2006). The hard drive had problems so I removed it, and now I'm trying to boot a Windows XP installation from a USB external drive. In the BIOS, I set the boot order to Hard Drive -> DVD drive -> Removable storage. There is no hard drive, and there is nothing in the DVD drive, so it should jump to removable storage, which I assume is USB drives? However, I plugged in the USB drive into one of the USB ports, and the PC doesn't boot from it.
I was able to hit "F8" on startup, which runs "BBS Popup", which lets me manually choose what to boot from, but only the DVD drive appears (since there is no HD).
Is there a compatibility issue, or something that I need to change in the BIOS, in order to make the USB external drive bootable in this older computer?
The computer may not support booting from a USB device. The option "Removable storage" may mean a floppy disk drive. When USB is supported as a boot device it's usually referred to as "USB" and/or shows the name of the USB device (if it's plugged in).
Or, it may be because the external hard drive's partition has been formatted to NTFS when it needs to be FAT32
Yeah the external drive is NTFS, but it's Windows XP so I assume that NTFS is necessary. You are probably right that "Removable storage" means Floppy. I ended up using Plop Boot Manager to boot from the USB drive (I had to enable "USB Legacy Support" in my BIOS first), then boot Windows XP from the external drive. Then I learned that you can't boot Windows XP from an external drive at all!