Porteus

Here's what happened:

1) I copied everything from my Porteus partition to an external (USB) HDD.
2) Installed SSD.
3) Copied everything back to new Porteus partition on SSD.
4) Cannot login. I get to login page, with guest in the name box, but won't login with guest as password (it was set up to automatically login before the move).

I can login as root, but this loses all my settings (which I have spent months honing to perfection).

I suspect it's a permissions issue (had the same problem with Linux Mint and it took me most of yesterday to sort out the mess I got into!).

Any fixes (please don't ask me to re-install!)?

can login as root, but this loses all my settings (which I have spent months honing to perfection).

It does indeed sound like a permission problem when you copied over the files. When you login to root try this from a console:
Then log out and try to log in as guest again.

Thanks, brokenman. I didn't get round to trying this because I gave up on Porteus for a day or two, then today tried to upgrade my Mint from 17.3 to 18, failed, went for a clean install of Mint 18, used its Grub to load Porteus and it logged in almost perfectly (except my settings had gone, but I can get those back as and when)!

Ha! Not as fixed as I'd thought. Keep arriving after automatic login at the keyboard selection dialogue: keep adjusting it but it's coming up every time. Also in file manager Guest > Desktop > New window > Guest > Desktop > New window > Guest > Desktop > New window loop. A real mess.