Screen appears briefly before losing connection
Screen appears briefly before losing connection
It's a common problem with two partitions or disks. I've experienced it before, so I suggest keeping one system on a single disk and leaving the others disconnected. It's cost-effective since the disks are inexpensive. This way, you avoid any trouble.
Actually, it's usually not a good idea to just reuse thermal paste like that.
Unless it's a Gen5 drive I wouldn't really be concerned. EDIT: if it's a Gen3 drive it doesn't really need it. EDIT 2: since this seems like an UEFI issue, you might want to boot from the Windows install USB and try fixing the current setup. See if that works and consider resetting the BIOS... even removing the GPU can help reset the UEFI.