Lolight

NicT,

the warning is just poorly worded legacy text from the older USB-to-USB transfer era.
Clicking "Yes" won’t physically nuke your drive; it just blacklists that specific USB's GUID on Unraid's activation servers so it can never be used for a USB-style license again.
Since you are moving to TPM (fTPM?) validation, Unraid will ignore the USB's GUID anyway, meaning you can keep booting off that exact same physical drive perfectly fine.
However, you should weigh the massive architectural risks of moving to a TPM license while keeping your OS on a USB drive.
You are essentially introducing the worst of both worlds:
The Firmware Landmine: Motherboard BIOS updates sometimes clear the fTPM or reset platform security keys.
If a future update alters your TPM cryptographic measurements, your Unraid license will suddenly show as invalid and lock you out of your array.
Total Loss of Portability: The best feature of Unraid has always been its disaster recovery. If your motherboard fries on a Sunday night, you used to be able to just move the USB stick to a spare PC and be back online in 5 minutes. If your license is locked to the TPM, a dead motherboard means your license is trapped in dead silicon until you go through a manual emergency transfer with Unraid support.
Double the Failure Points: You will still be exposed to the physical unreliability and heat degradation of a consumer USB drive holding your OS files, plus the hardware lock-in and firmware fragility of a motherboard TPM holding your license.
If you want true portability and safety, you are much better off sticking to a USB-bound license, but upgrading the physical hardware to a real industrial-grade MLC USB drive (like a liquidated Innodisk 3ME currently on super sale) plugged into a USB 2.0 port.

This is purely a boot drive issue and fully recoverable.
Use the Unraid USB Creator to create a fresh bootable drive on a new USB, selecting the current stable version (6.12.15 is fine -- you can update from within Unraid afterward).
Then copy your config folder from your flashbackup to the new USB, replacing what the Creator put there. That's it.

A few notes:
-- Don't copy everything from the flashbackup, just the config folder
-- The new drive will have a different GUID so you'll need to transfer your license. You get one self-service transfer per year via the Unraid Connect portal.
-- Once back up, avoid USB 3.x ports for boot.
-- While you're sourcing a replacement, check the Unraid Boot Devices Guide guide in the Boot Devices section of this forum.

If in a hurry, get Innodisk DEUA1-64GI61BW1SC -- industrial grade, around $4, plug into a USB 2.0 port.
Worth getting a couple while they're available at that price. eBay item number: 326046070546

The process starts with backing up your existing drive through Main --> Boot Device --> Boot Device Backup.
Then use the USB Flash Creator -- select "Use custom" option and point it at the backup ZIP file.
This copies your existing configuration and license key across to the new drive rather than writing a fresh installation.

Boot from the new drive.
Go to Tools --> Registration and click Replace Key.
This transfers the license association from the old drive's GUID to the new drive's GUID on Lime Technology's license server.
The old drive gets blacklisted automatically.

The automated transfer is available once per year.
If you need another within 12 months contact support directly.
Worth checking the USB Flash section guide before selecting your new drive -- it covers what makes a reliable boot drive for always-on server duty.

Good find on the PNY Attache.
Since you're on a trial the sequence is slightly different from a paid license transfer — trials can't be transferred, only paid licenses can.

Cleanest path:
Back up your current SanDisk drive through Main --> Boot Device --> Boot Device Backup.
Use the USB Flash Creator on the PNY drive -- select "Use custom" and point it at your backup ZIP file.
This migrates your entire configuration across automatically.
Boot with the PNY drive.
Purchase the license and register it on the PNY drive through Tools --> Registration.
The SanDisk gets left behind rather than blacklisted -- trial licenses don't trigger the blacklist mechanism that paid license transfers do.

One question — have you already purchased the PNY drive?
If not share the eBay listing here for a quick check.
The specific model and production era matter -- not counterfeit risk with genuine NOS drives, but making sure the listing is actually the right vintage rather than a later production drive described loosely as old stock.

Thank you for the response.