BEV stands for Bootstrap Entry Vector. From http://www.scs.stanford.edu/nyu/04fa/lab/specsbbs101.pdf
A Bootstrap Entry Vector is a pointer that points to code inside an option ROM that
will directly load an O/S. The BEV resides in a PnP option ROM Expansion Header.
An example of an option ROM with a BEV is a PnP ISA ethernet controller.
It's a method a device like a network card used to boot your PC from that device. As a concrete example, I believe PXE booting (which is a common way to bootstrap a PC over the network), starts with the BEV field on the network card.
About the flash drive. I feel like getting a random USB stick to boot on a random computer has always started off with frustration. Here's what I would try (this isn't solid advice so much as my random collection of troubleshooting tips).
- Be absolutely sure you can boot off the USB stick on another PC (don't use a Mac). Basically verify your stick is bootable. Make a note of how that USB stick appears to the BIOS of that computer. Is it a USB CD-ROM? A USB hard drive? Something else?
- Go look at the USB settings in your BIOS. You're looking for something that might indicate you can turn on/off booting from USB.
- Verify the port you're trying to boot from is active. Some PCs have multiple USB controllers (rear ports might be different than front ports) and not all of them may be active by default or bootable by default.
- From BIOS, with the USB stick plugged in, see if it shows up in any list of devices.