I re-installed Windows because my C: drive (512GB) was full to the brim, though I have no idea why. This happened after I processed the photos.
So I reinstalled Windows and my C: drive is 100% full again - after running the photo exports, even though all the original photos, all the exported photos, and ON1 are all installed on a different physical drive.
No clue why this is happening - I had less than 100GB installed on that drive only to find it completely full this morning.
This is another fun aspect of Photo RAW: lots of stuff accumulates in various databases. Try looking here ...
%userprofile%\AppData\Roaming\ON1\ON1 Photo RAW 2025/PhotoSettingsCache
... and see how much space the folder is taking up. Once you're done processing, you don't really need that stuff anymore and you can delete the contents of the folder. They will be rebuilt again as necessary, and you can then delete them again. Do it while the app is closed.
I don't know if that's the only thing happening on your system, but it's probably one thing that's happening.
If you use cataloged folders, keywords, custom metadata, etc., there will also be disk space taken up for that stuff, somewhere else.
