Gyro, as you mentioned SSD alignment, I thought I'd report back with this. XP has been running fine, but I hadn't aligned the SSD, so I removed it, connected it to my W10 machine and deleted the volume, created a new one and formatted it, as W10 should do this, aligning the SSD.
Put it back in the legacy laptop, installed XP and encountered disk read errors once the installation wanted to reboot......
Restarted XP installation and used that to delete the volume, create and format, installed and it's fine....
Any thoughts on why it doesn't like to be pre formatted elsewhere?