Deleting system-reserved Partition on second drive in order to convert from MBR to GPT

Solution 1:

Your terminology is wrong:

First, each of your four disks is apparently of MBR format. There is a separate MBR for each disk. Starting with Windows 10 version 1703, you may convert any disk to GPT with no data lose, but then getting Windows to boot is another matter.

Second, converting to UEFI would most likely require to do Repair Install of Windows 10 with an In-place Upgrade using a UEFI boot media of Windows, as Windows itself wouldn't boot after the conversion. You would also need space for the EFI partition, although the Repair Install would probably take care of it automatically.

Third and most important, installing Linux in dual-boot configuration with Windows does not require UEFI or GPT. You may install it on your disks in your current configuration. Just use a Legacy BIOS boot media for installing Linux. The dual-boot installation would use the Linux GRUB instead of UEFI, but would work just as well.

Fourth, take strong backups before doing such operations, because there is always the risk of making Windows unbootable.

Last, if your intention is to test Linux, you may install it inside Windows using the Windows Subsystem for Linux (WSL), without taking any risks with your data.