The customer has a Dell Precision with Win 10 Pro installed. After deleting the partition and formatting the HDD, the installation runs without a problem, but the boot device is not found. Bios is set to UEFI, and if I change it to Legacy Boot, it boots and loads fine. When it fails, Dell Pro Support says we need to format the drive in GPT. If we let it continue to boot in Legacy, do we run into problems ... looks good now?
There are two configurations for Windows 10: Legacy BIOS and UEFI boot option. But which boot mode to use depends mainly on your Windows partitioning method.
Extended Reading: UEFI vs. BIOS: What's the Difference and Which is Better
Usually, booting in Legacy mode will not cause any problems. However, Legacy boot mode does not support partitions larger than 2TB in size, and it may cause data loss or other problems if you try to use it normally. If you have set the Legacy boot option in BIOS, the drive partition table may be the master boot record (MBR).
You do not need to format your HDD on another computer. Or convert the MBR to GPT unless you require a boot partition that is more than 2 TB in size. In GPT mode, you need to use the UEFI boot mode. Also, you need to be aware that manually formatting the drive before installation may cause problems if you do not configure the correct partition classification.
If you want to convert MBR to GPT and boot from BIOS, you can try EaseUS Partition Master. This professional tool is designed for disk converters.
Click the following link for detailed steps and guides to convert the disk.
Further Reading: How to Convert MBR to GPT or GPT to MBR Without Losing Data in Windows 11/10/8/7
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