If a VMware VM will not boot after a VHD-to-VMDK conversion, first identify where startup fails: at firmware, with “Operating system not found,” or after Windows begins loading with INACCESSIBLE_BOOT_DEVICE. Those symptoms point to different causes. Check the virtual storage controller and its guest driver for a Windows stop error; check firmware mode, partition layout, and boot files for a missing operating system message. Back up or clone the disk before changing firmware, partitions, VMDK metadata, or boot files.
First identify the error and what was converted
Record the complete console message or stop code, then determine whether you converted only a disk image or migrated a whole machine with VMware Converter or another P2V workflow. Broadcom’s support cases cited below primarily address Converter/P2V outcomes; their remedies are not automatically applicable to every VHD-to-VMDK utility.
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- Fails before the guest starts: inspect the VM’s firmware setting and boot-device configuration.
- “Operating system not found” or “Operating System not found”: check the boot disk, partition scheme, and bootloader. The conversion may have copied the data successfully while leaving the VM without a usable boot path.
- Windows reaches startup and shows
INACCESSIBLE_BOOT_DEVICE: check whether Windows can access the virtual storage controller assigned to the VM. - Black screen or a disk-read message: note the exact wording and guest OS before attempting repairs; older Windows P2V reports describe causes that do not apply universally.
Keep a known-good copy of the original VHD and the converted VMDK. A repair that changes partitioning or boot files can make recovery harder if it targets the wrong disk.
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After P2V, Windows can fail with INACCESSIBLE_BOOT_DEVICE when the guest lacks an enabled driver for the virtual storage controller used by the VM. Broadcom documents a case where the required driver was not injected or active during early boot. The relevant question is not simply whether Windows has a storage driver somewhere: it must be available when Windows starts from this boot disk. Broadcom’s P2V troubleshooting article discusses this failure mode and offline driver injection.
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- In the VM’s settings, identify the controller to which the boot disk is attached. Common examples include LSI Logic SAS and VMware Paravirtual (PVSCSI).
- Check that the Windows installation has the driver required for that controller and that the boot disk is attached to the controller Windows expects.
- If the driver is missing or inactive, treat offline injection through Windows Recovery Environment (WinRE) or Windows installation media as an advanced OS repair. Follow instructions for the exact Windows version and VMware release; do not change controller types casually on a non-booting machine.
Broadcom also has a separate article about VMDK descriptor adapter types and Storage vMotion. It discusses historical guest-specific examples and says that when PVSCSI is desired, the descriptor setting should be lsilogic; it warns that PVSCSI as the descriptor’s ddb.adapterType can cause Storage vMotion failure. This is not a general instruction to edit a VMDK descriptor to fix a boot error. Preserve a copy and use guidance for your VMware release before making descriptor changes. See Broadcom’s VMDK adapter-type guidance.
Fix “Operating system not found” by matching firmware and disk layout
Check the VM’s firmware mode against the converted disk’s partition scheme and boot files. BIOS/legacy boot and EFI/UEFI boot use different boot arrangements. Changing the VM from one firmware mode to the other does not convert MBR to GPT or create the required boot files.
Broadcom’s firmware article, for vSphere 7.x and 8.x, describes this expected behavior: “This is an expected behavior as BIOS uses MBR (Master Boot Record) partitioning and EFI requires GPT (GUID Partition Table) partitioning on the VM disks.” Its case is specifically a VM made unbootable after changing firmware from BIOS to EFI. Read the Broadcom firmware-change article.
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- Check that the guest OS supports the intended firmware mode and that its bootloader is configured for it.
- If the modes and disk layout do not match, use a supported conversion or rebuild path for that OS and VMware version. Make a backup first; do not switch firmware back and forth as a substitute for correcting the boot setup.
Broadcom separately warns against switching Legacy BIOS to UEFI before converting MBR to GPT in its Secure Boot guidance. See the Secure Boot and firmware guidance.
Linux: treat the CentOS 7 case as a specific example
A Broadcom case involving a CentOS 7 conversion describes an MBR output disk despite a more complex source boot setup, resulting in an EFI/bootloader mismatch. Its resolution discusses BIOS and GRUB repair for that scenario. It is not evidence that every Linux VHD conversion should be switched to BIOS or repaired the same way. Verify the source and destination boot configuration before applying Linux-specific commands. Read the CentOS 7 conversion case.
Repair missing Windows EFI boot files only after confirming the partition
A missing or corrupt EFI partition—or a conversion that included an unexpected recovery partition—can leave a Windows VM unable to boot. In one P2V case, Broadcom describes booting Windows media and rebuilding EFI boot files with bcdboot. The article also discusses partition operations, which can destroy data if applied to the wrong disk or partition. See Broadcom’s EFI-partition repair case.
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- Back up or clone the VM disk before modifying partitions or boot files.
- Boot from Windows installation or recovery media and confirm which disk and partition are the EFI system partition. Do not assume a partition number from another machine applies to yours.
- Use
bcdbootonly with the correct Windows installation and EFI partition, following instructions appropriate to the installed Windows version and the VM’s firmware mode.
Windows recovery media is needed for this route. Follow Microsoft’s current requirements for creating and using installation media; the Broadcom case is not a universal partition-repair recipe.
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For VMware Converter workflows, Broadcom’s checklist recommends checking disk health before conversion, not installing VMware Tools during conversion, and checking the configured virtual SCSI controller if the converted VM blue-screens. It also points to Windows ISO repair. These are Converter troubleshooting recommendations, not a guarantee that a disk-only VHD conversion will boot. Read Broadcom’s Converter troubleshooting checklist.
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Two older Windows P2V causes are worth checking only when the OS generation and symptom fit: a /burnmemory entry in boot.ini associated with a black screen, and boot.ini/ARC-path problems described in a legacy Converter article. Do not treat either as a likely universal explanation for current Windows guests. Broadcom’s black-screen case and its legacy boot.ini/ARC-path article describe those scenarios.
Choose the repair by symptom, not by the file extension
| What you see | First check | What the evidence supports |
|---|---|---|
Windows INACCESSIBLE_BOOT_DEVICE |
Virtual storage controller, boot-disk attachment, and early-boot driver | Broadcom documents a P2V case involving a missing or inactive controller driver. |
| “Operating system not found” | Firmware mode, MBR/GPT layout, boot partition, and bootloader | Broadcom documents firmware/partition mismatches and specific EFI repair cases. |
| Windows EFI boot failure | Whether the EFI system partition and boot files exist and correspond to the Windows installation | A Broadcom P2V case uses Windows media and bcdboot; its partition operations are case-specific. |
| Black screen on an older Windows guest | Whether the guest and configuration match the documented boot.ini scenarios |
Older Broadcom reports discuss /burnmemory and ARC paths; they should not be generalized to modern systems. |
If the symptom does not match a documented scenario, stop before applying its repair steps. Confirm the conversion method, guest OS, firmware, partition scheme, and controller first, then use documentation for that exact configuration.
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