Your PC Ignores the MediCat USB and Boots into Windows
The pendrive is created correctly, you restart — and Windows loads as if the USB does not exist. Or a red 'Secure Boot violation' message appears. Both are BIOS/UEFI settings problems, not MediCat problems, and both are fixable in a few minutes.
✍️ Technical Anshu🪟 Windows 10 / 11⏱️ 8 minute read
🎥 Watch the USB being selected at boot in the video, from power-on to menu
A bootable USB only works if the computer is told to use it. Modern PCs add a second gatekeeper: Secure Boot, which refuses to start any bootloader it does not recognise. Ventoy (which powers MediCat) can work with Secure Boot on many machines, but when it cannot, the fixes are standard. Work through them in order — most people succeed at Fix 1 or 2.
Secure Boot Violation
Invalid signature detected. Check Secure Boot Policy in Setup
OK
The real message many machines show when Secure Boot refuses the Ventoy bootloader. Nothing is broken — a BIOS setting is doing its job. Fix 2 handles it.
1
Use the One-Time Boot Menu — Don't Wait for It to 'Just Boot'
Many PCs never boot USB automatically; you must ask at power-on:
Plug the MediCat USB in before switching the PC on.
Power on and immediately tap the boot-menu key repeatedly: commonly F12 (Dell, Lenovo), F8 or F11, Esc (HP), or F9 on some HP models. If one key does nothing, try the next — brands differ.
In the menu, choose the entry with your USB drive's name — on UEFI systems it may appear as UEFI: <drive name>. That is your MediCat/Ventoy entry.
The Ventoy menu should appear within seconds. If you instead land in Windows, you missed the timing — restart and tap the key earlier and faster.
Please select boot device:
UEFI: USB Flash Drive Windows Boot Manager Enter Setup
A typical one-time boot menu (names vary by brand). The USB entry is the one that starts MediCat; 'Windows Boot Manager' is the one that ignores it.
2
Secure Boot Is Blocking It — Turn It Off (or Enrol Ventoy's Key)
If you see "Secure Boot Violation", "Invalid signature detected", or the USB entry simply refuses to start, Secure Boot is the cause:
Restart and enter BIOS/UEFI setup (usually F2 or Del at power-on).
Find Secure Boot — typically under the Boot or Security tab — and set it to Disabled. Save and exit (usually F10).
Boot the USB from the boot menu again. MediCat should now start.
Alternative on many machines: Ventoy offers a Secure Boot support option, and on first boot it may show a blue key-enrolment screen (MOK Manager) where you enrol Ventoy's key once, after which it boots with Secure Boot left on. If that screen appears, follow its enrolment steps; if it never appears or fails on your model, disabling Secure Boot is the practical route.
After your repair work is done, you can turn Secure Boot back on for normal Windows use.
3
Set the Boot Order (Only If You Boot USB Often)
The one-time menu is enough for a single repair. If the boot menu key is unreliable on your machine, change the order instead:
Enter BIOS/UEFI setup (F2 / Del).
Open the Boot tab and move the USB drive / UEFI USB entry to the top of the boot priority list.
Also confirm any setting named USB Boot or External Device Boot is Enabled — some laptops ship with it off.
Save, exit, and restart with the USB plugged in.
4
USB Shows in Menu but a Tool Fails or Screen Goes Weird
Different symptom, quick checks:
Tiny 640x480 resolution in Mini Windows: a known quirk on some laptops when the drive was created with Ventoy's Secure Boot support enabled. Re-creating the drive in Ventoy with Secure Boot Support unchecked has fixed this for many users.
Menu appears but one image errors: that single file may be corrupted — re-copy just that file to the drive from your PC copy and try again.
Nothing at all, on an old PC: very old BIOS-only machines can struggle with some partition layouts. If you create the drive with Ventoy manually, the MBR partition style is the most compatible choice for mixed old and new hardware.
5
Confirm the Drive Itself on a Second PC
Before changing more settings, separate "PC problem" from "USB problem":
Plug the MediCat drive into any other computer and open its boot menu.
If Ventoy's menu appears there, your drive is perfect — the first PC's BIOS settings are the whole problem. Go back to Fixes 1-3 on that PC.
If no PC can boot it, the drive creation failed (often an interrupted copy or an antivirus-deleted file). Re-create it using the full install guide, with antivirus paused during the copy.
The video above shows a successful first boot end-to-end — the boot-menu selection and the Ventoy screen you should see. Compare your PC's behaviour step by step.
🔴 Reality check: disabling Secure Boot to run a repair toolkit is a normal, reversible technician step. Just remember to switch it back on afterwards, and never leave a customer's PC with it disabled without telling them.
🎥 Watch the Complete Process in the Video
Watch the correct boot sequence in the video — power-on, boot key, USB selection, Ventoy menu.
For a repair session, yes — technicians do it routinely, and you can re-enable it afterwards in the same BIOS menu. Secure Boot protects your normal Windows startup; while it is off, only boot media you trust, like your own MediCat drive.
My laptop has no USB option in the boot menu at all. Why?
Usually one of three reasons: the USB was plugged in after power-on (restart with it inserted), USB Boot is disabled in BIOS settings, or the drive itself is not bootable because its creation was interrupted. Test the drive on another PC to separate the causes.
Do I need to change boot order permanently?
No. The one-time boot menu (F12 and similar keys) is designed exactly for this and changes nothing permanently. Change the boot order only if the one-time menu does not work on your machine.
This guide is based on the Technical Anshu MediCat USB video • Stuck on any step? Ask in the video comments — help is available there 🙏