Migrating a Windows VM from VMware to Proxmox? Don't Lose Your Windows Server Activation. Microsoft retired telephone activation as of December 2025. Users are redirected to an online portal (aka[.]ms/aoh) that requires a Microsoft Account. You log in, type in your Installation ID (generated on the server by running slui 4), and it attempts to generate a Confirmation ID for you. If you have a Retail or Volume License (MAK) key and you are simply doing a clean install or an offline activation on the exact same hardware, the portal will generally work. It will process the Installation ID and hand back a Confirmation ID to activate the server.
An already-activated (non-KMS) Windows stores its activation in tokens.dat, which rode along with the VM's disk during the conversion. At boot, Windows re-validates that stored activation against the current hardware locally. Match the SMBIOS UUID (plus MAC/SMBIOS strings) to what VMware presented, and the existing activation re-validates with zero server contact.
Here's how to do it (assuming a Retail / MAK / Volume license):
Step 1 — Check your license type. In the guest, run slmgr /dlv. If it's KMS, it re-activates automatically — you're done. If it's Retail or MAK, keep going.
Step 2 — Grab the original UUID from your .vmx. Find the uuid.bios line, e.g.: uuid.bios = "56 4d 59 5c 4c 56 4b 10-b8 e0 66 84 d3 2d 01 63"
Step 3 — Fix the byte order: SMBIOS stores the first three UUID fields little-endian. Reverse the byte order within groups 1–3 only. Those example bytes become: 5c594d56-564c-104b-b8e0-6684d32d0163 Copying the raw string left-to-right gives the WRONG UUID and breaks activation.
Step 4 — Apply it in Proxmox. Edit /etc/pve/qemu-server/<VMID>.conf and set: smbios1: uuid=5c594d56-564c-104b-b8e0-6684d32d0163
**(Or enter it via the web UI under Options → SMBIOS settings.)
Step 5 — Match the MAC address. Copy ethernet0.address from the .vmx onto your net0 line so the NIC identity carries over too. (*note: you can preserve the ethernet MAC address during the VMw-to-Pmx conversion)
Step 6 — Verify inside the guest. Boot the VM and run: wmic path win32_computersystemproduct get uuid.
Confirm it matches your target, then check slmgr /xpr.
One caveat: if your .vmx contains SMBIOS.reflectHost = "TRUE", the VM was mirroring the physical ESXi host's SMBIOS (common with OEM/ROK licenses).
In that case you'll need to replicate the host's manufacturer strings and its SLIC/MSDM ACPI table instead — a different process.
And remember: you own the license. If a MAK/Retail key still shows unactivated after matching the hardware, online reactivation is completely legitimate.
Moving off VMware doesn't have to mean re-licensing your legacy Windows Server OS, but there's some techical work involved in making it function properly.
An already-activated (non-KMS) Windows stores its activation in tokens.dat, which rode along with the VM's disk during the conversion. At boot, Windows re-validates that stored activation against the current hardware locally. Match the SMBIOS UUID (plus MAC/SMBIOS strings) to what VMware presented, and the existing activation re-validates with zero server contact.
Here's how to do it (assuming a Retail / MAK / Volume license):
Step 1 — Check your license type. In the guest, run slmgr /dlv. If it's KMS, it re-activates automatically — you're done. If it's Retail or MAK, keep going.
Step 2 — Grab the original UUID from your .vmx. Find the uuid.bios line, e.g.: uuid.bios = "56 4d 59 5c 4c 56 4b 10-b8 e0 66 84 d3 2d 01 63"
Step 3 — Fix the byte order: SMBIOS stores the first three UUID fields little-endian. Reverse the byte order within groups 1–3 only. Those example bytes become: 5c594d56-564c-104b-b8e0-6684d32d0163 Copying the raw string left-to-right gives the WRONG UUID and breaks activation.
Step 4 — Apply it in Proxmox. Edit /etc/pve/qemu-server/<VMID>.conf and set: smbios1: uuid=5c594d56-564c-104b-b8e0-6684d32d0163
**(Or enter it via the web UI under Options → SMBIOS settings.)
Step 5 — Match the MAC address. Copy ethernet0.address from the .vmx onto your net0 line so the NIC identity carries over too. (*note: you can preserve the ethernet MAC address during the VMw-to-Pmx conversion)
Step 6 — Verify inside the guest. Boot the VM and run: wmic path win32_computersystemproduct get uuid.
Confirm it matches your target, then check slmgr /xpr.
One caveat: if your .vmx contains SMBIOS.reflectHost = "TRUE", the VM was mirroring the physical ESXi host's SMBIOS (common with OEM/ROK licenses).
In that case you'll need to replicate the host's manufacturer strings and its SLIC/MSDM ACPI table instead — a different process.
And remember: you own the license. If a MAK/Retail key still shows unactivated after matching the hardware, online reactivation is completely legitimate.
Moving off VMware doesn't have to mean re-licensing your legacy Windows Server OS, but there's some techical work involved in making it function properly.
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