I just recalled something I did to my Windows (8.1) back when I experienced bad TS4 lagging. I switched off the Win feature that constantly indexes all folders on the explorer system. It is a background task that I believe not many are aware of. It runs in the background occasionally to make your experience better and faster when you search within folder/s. Perhaps a function also some programs benefits from, but I think most programs will do their main indexing as they load anyway. After this, I have much less periodic lag while running the game, and the only backside I noticed is that when I open a explorer folder it might take a few seconds to list the content, and if I search for filename (very rarely) it might take 10 seconds because Win will do the full indexing of that folder or folder group.
I know thee are more Windows tasks working in the background and a little googling will find them. No idea if they are all in Win10 and newer. Shutting them down may not free up much space on C drive, but might still help on performance, and I believe running background tasks will have a worse effect when the C drive is full.
