Tx for the info. It'd be useful to label the error so one would know if an operation had failed or whether it's a precautionary warning that something could fail due to the lack of space.
I've just noticed that something has changed my Windows env variables for TMP and TEMP back to C:
Does mp3tag use those?
Unfortunately diagnosing what is writing to C: is difficult, even with the assistance of Windirstat, Spacesniffer etc.
Nvidia drivers storing up historical driver downloads, MS Edge saving huge amounts of data even though I don't use it, AV apps squirreling away folders full of hundreds of tiny files containing what I have no clue, installers unzipping into root folders ...
Basically it seems all the developers have huge drives and have no need to care! I went from 120GB to 240GB and thought all my problems would be solved but it appears not.
It'd be great if the OS devs could mandate clearly separate places for app images, temp workspace, config, data etc. but I know it's a hopeless dream!
But I didn't know mp3tag could be run as a portable app (I've not really considered that as an option before and I see the install prompts about it!) so I'll look into that too.