Trouble with a bootable USB drive

Greetings,
I created a bootable USB drive today using Adobe Flash containing Windows 7. I am fully aware that I need to set this USB as the primary boot option within the BIOS settings.
However, when I restart my machine with the USB plugged in and access the boot menu, this is what I see:

1. SATA 0 CD/DVD.......
2. SATA 1 HDD.......
3. PCI DEVICE.........
4.
5.
6.
Excluded from boot:
-Legacy device....
-some bootable cards

The point is—there is no removable device listed, nor is there any sign of the USB.
My BIOS is Dell // Phoenix Technologies Ltd. 6.00 R1.12.2584.A1
running on a Dell OptiPlex motherboard.
If anyone can provide assistance, I would be grateful.

Is this a desktop or a laptop? Just a heads up, that isn't actually a motherboard model number, it's just the name of the Dell OptiPlex

Joshua Garcia3 said:Is this a desktop or a laptop? That isn't the motherboard model—it’s the model for the Dell OptiPlex itself.

It is a desktop PC—and that is exactly what CPU-Z shows for the motherboard.

Maybe it just won't boot from a USB drive... Honestly, you might be better off burning it to a blank CD-DVD and calling it a day.

Did you actually set the primary boot device within the BIOS settings itself, or did you just pick it from the one-time boot menu after hitting restart?

Make sure you aren't accidentally using a USB 3.0 port?

I haven't set it as the primary boot device—mostly because the BIOS won't even recognize it under the boot tab.
I'm using a USB 2.0 port.

To get into the BIOS, you just tap the Del key, F1 through F12, or Esc—whatever your specific machine prompts you with on the startup screen. Once you're in, you can actually manage which devices show up in that boot menu. Most likely, your USB device has been disabled in the settings. You won't see it as a boot option during the next restart until you go in there and enable it. Good luck.

Andrew Fowler49 said:You access the BIOS using Del, F1-F12, or Esc—whatever your specific system prompts you with during startup. Once inside, you can select which devices should appear in your boot menu. It is highly probable that your USB device is currently disabled. Only after you enable it will it show up as an option when you restart the computer. Good luck.

I am already aware of that—it simply isn't appearing in the menu. Regardless, thanks.

Alright... give it a shot by heading into the BIOS and switching from UEFI to Legacy mode, or just try disabling Secure Boot altogether. That might actually get the USB to behave.

Andrew Fowler49 said:Alright... try switching from UEFI to Legacy mode in the BIOS—or just disable Secure Boot—maybe then the USB will actually work.

The boot menu only shows what I listed above along with a help option on the side—but there is that "excluded from boot" Legacy entry I mentioned in my first post. As for Secure Boot, it isn't even an option here.