Solved the speaker/audio output issue, but had to make changes to alsamixer through the command line.
Works for Fedora, LMDE and Mint Mate. The sound card has switchable outputs to front and rear, and under windows the switching is automatic, but with Linux it requires a manual switch using the alsamixer command which then pops up a pseudo GUI that allows changes to be made that aren't available on the DE. I could hear the internal relay switching the output between front and rear sockets every time I manually toggled between the options.
I was also reminded why I'd not used Fedora more in the past - almost all useful codecs have to be installed from non-standard repositories, and it's a pain in the bum to sort out. Want to play back MP3 files - need a codec. Want to watch DVDs - need a codec. etc. It used to be worse, when using a dialup modem needed custom-written drivers, and although the OS was free, the drivers cost a small fortune.
LMDE is interesting, but the installer has been fiddled with since last time and it wanted me to set up partitions manually. It's been a while since I last did that and GParted didn't always behave as I'd remembered either, so that one is parked for now, though I really like the idea of a faster, lighter OS.
Mint Mate went in painlessly on the testing HDD. I'll keep it there for week or so to see how it does before replacing the questionable drive.