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The following guide documents BootGuard error BG-2TB and provides a resolution to the boot-time error screen presenting this problem.
<h3>BootGuard Error BG-2TB</h3>
When booting from a PC that has been protected by NeoSmart Technologies'<sup style="font-size: 60%;"> ® </sup> BootGuard™ technology on a PC that has been configured to start up in legacy/MBR/CSM mode, the following message with error code BG-2TB may be displayed:

<img class="aligncenter size-full wp-image-5259" src="https://neosmart.net/wiki/wp-content/uploads/sites/5/2016/03/BG-2TB.png" alt="" width="800" height="600" />
<blockquote>BootGuard by NeoSmart Technologies

This PC has been prevented from booting in legacy mode to protect your data.
Please re-configure your UEFI firmware (aka "BIOS setup") to boot in UEFI mode.

Error Code: BG-2TB
More Information: http://neosmart.net/wiki/bootguard-2tb/

Press CTRL+ALT+DEL to restart</blockquote>
<h3>What is BootGuard™?</h3>
BootGuard™ is a boot-time helper that is installed to the MBR of your boot disk in order to protect you from accidental data loss due to a misconfigured PC. It is normally installed as part of an automated boot initialization or  repair procedure, such as our Easy Recovery Essentials<sup style="font-size: 60%;"> ®</sup> bootable Windows repair and recovery CDs. BootGuard is normally 100% invisible, and only kicks-in if it detects a problem with your boot configuration, preventing from using your computer in a way that might trigger data loss.
<h3>BootGuard error BG-2TB</h3>
The specific BootGuard error BG-2TB is shown when the disks in your PC have been configured with partitions greater than 2TiB in size. ((More specifically, the limitation does not refer to the actual size of any partition, but rather the presence of valid, data-containing partitions that extend past the 2TiB mark, regardless of the actual size of the partition itself.)) Traditional <a href="http://neosmart.net/wiki/mbr-boot-process/">BIOS/MBR PCs</a> use a standard that dates back to the early 1980s, and cannot comprehend nor handle disks larger than 2TiB. In order to fully utilize a disk that's larger than 2TiB or to have a partition that is larger than 2TiB, the newer GPT disk layout scheme must be used - and your PC must be configured to boot in "UEFI mode" in order to do so.

Older PCs cannot normally boot from a GPT disk at all; EasyRE enables your PC to boot in both traditional BIOS/MBR mode or in UEFI/GPT mode so long as you do not have a partition that extends past 2TiB. However, if you try to boot into a system with a partition larger than 2TiB, BootGuard error BG-2TB is shown to prevent your PC from data loss.
<h3>What happens if you boot in MBR mode with partitions larger than 2TB?</h3>
Without BootGuard and with your PC set to boot in legacy/MBR mode, any partitions that extend past the 2TB mark will appear truncated to the operating system. In the best case scenario, you'll only be able to use the first 2TB of your partition - but this is unfortunately rarely what actually happens. The space in your partition isn't filled up from beginning to end, most PCs use an <a class="cboxElement" href="https://neosmart.net/blog/wp-content/uploads/sites/5/2016/03/If-I-Fits-I-Sits.jpg">"if it fits, it sits" approach</a> meaning that wherever free space is found on the partition, your data will be stored. This means that "partially opening" a partition and taking only its first 2TiB can complete corrupt and permanently lose your data! BootGuard intercepts attempts to boot the PC under these conditions, and reminds you to re-configure your PC to boot in UEFI mode instead.
<h3>How to fix BootGuard error BG-2TB</h3>
The solution is quite simple: you need to enter your firmware setup/configuration utility (more commonly, if incorrectly, known as BIOS setup) and set up your PC to boot in UEFI mode. We have published detailed instructions on how you can <a href="https://neosmart.net/wiki/enable-uefi-boot/">disable legacy boot and make sure your PC is booting in UEFI mode</a> on your UEFI-capable PC in our knowledgebase.

Make sure that if your PC supports both UEFI and Legacy/CSM boot modes simultaneously that it is configured to prioritize UEFI booting.