MemTest86+ - Test RAM  

Fergo mate you could have a play with the secure boot and CSM settings and even try a CD instead of the stick - just a thought as you can just revert the secure boot and CSM settings afterwards or if it doesn't work.

Make sure these things are disabled if your UEFI/BIOS has the equivalent:

Windows 8.1/ 10 WHQL Support [Disabled]
Enables the supports for Windows 8.1/ 10 or disables for other operating systems.
Before enabling this item, make sure all installed devices & utilities (hardware &
software) should meet the Windows 8.1/ 10 requirements.
[Enabled] The system will switch to UEFI mode to meet the Windows
requirement.
[Disabled] Disables this function.


MSI Fast Boot [Disabled]
MSI Fast Boot is the fastest way to boot the system. It will disable more devices to
speed up system boot time which is faster than the boot time of Fast Boot.
[Enabled] Enables the MSI Fast Boot function to speed up booting time. And
the following Fast Boot field will be disabled and fixed.
[Disabled] Disables MSI Fast Boot.


Fast Boot [Disabled/ windows7, Enabled/ windows 8.1/ 10]
Enables or disables the fast boot feature for Windows 8.1/ 10. This item will only be
available when MSI Fast Boot is disabled.
[Enabled] Enables the Fast Boot configuration to accelerate system boot time.
[Disabled] Disables the Fast Boot configuration.


Secure Boot
Sets the Windows secure boot to prevent the unauthorized accessing. Press
<Enter> to enter the sub-menu. This sub-menu will appear when Windows 8.1/ 10
WHQL Support is enabled.


Secure Boot Support [Disabled]
Enables or disables secure boot support.
[Enabled] Enables the secure boot function and allow you to set the secure
boot settings.
[Disabled] Disables this function.


Secure Boot Mode [Standard]
Selects the secure boot mode. This item is to select how the secure boot keys be
loaded. This item appears when Secure Boot Support is enabled.
[Standard] The system will automatically load the secure keys from BIOS.
[Custom] Allows user to configure the secure boot settings and manually load
the secure keys.


Boot Mode Select [LEGACY+UEFI]
Sets the system boot mode from legacy or UEFI architecture depending on OS
installation requirement. This item will become un-selectable and will be configured
automatically by BIOS when Windows 8.1/ 10 WHQL Support is enabled.
[UEFI] Enables UEFI BIOS boot mode support only.
[LEGACY+UEFI] Enables both Legacy BIOS boot mode and UEFI BIOS boot
mode.

FerchogtX said:

Just as update, changing to legacy boot worked, I can see the USB in the boot menu, I will finish stuff and leave this overnight, I hope it survives XD.

Thank you!

You're welcome:)

By the way there is a new version:

Version 7.4 26/July/2017

Fixes/Enhancements

• Added new file blacklist.cfg that contains a list of baseboards that have known MemTest86 boot issues
• Added 'CONSOLEMODE' config file parameter for specifying the mode of the UEFI console. Setting the console mode determines the resolution of the console (with 0 being the minimum supported resolution of 80x25)
• Added 'BITFADESECS' config file parameter for specifying the sleep interval in the Bit Fade test (Test 10)
• Added language support for Catalan
• Updated ImageUSB to version 1.3
• Fixed 128-byte alignment issues in the random library
• Errors detected in Test 12 (128-bit Random Number Sequence Test) are now logged as 128-bit values
• HTML test report now includes if ECC polling was enabled
• Fixed text artifacts appearing in the testing screen due to the text being too long
• Fixed memory size being incorrectly reported due to including non-RAM memory ranges (eg. NVM, MMIO, Reserved)
• Fixed main menu screen being too small due to resolution being set too high
• Added preliminary ECC Injection support for Intel Xeon E5 chipsets
• Added preliminary ECC Injection support for Intel D-1500 chipsets
• Added ECC detection support for different variations of Intel Kaby Lake chipset
• Added support for retrieving AMD Ryzen CPU info, including base and turbo clock speeds
• Improved the performance and robustness of measuring CPU base/turbo speeds for AMD chipsets
• Updated JEDEC RAM manufacturer ID list
• Added reset mechanism for Intel ICH SMBus when timeout occurs while accessing SPD registers
• Fixed DDR4 SPD data not being read for PIIX4 SMBus controllers

Stick to single core, as multicore has been reported as relatively unstable, and causes false positives.
Theoretically it's suppose to make checks faster, but faster is also less stable.