This started happening yesterday. Whenever I download a game from steam after a couple of minutes my whole system starts to hang (mouse lags, audio lags, programs lag) and I get high CPU usage in windows explorer, Avast, System Interrupts, and Steam. I've read a couple places that it may be Avast scanning every single file, but I've disabled all functionality down to just the scanner and even disabled the shield and still the hangs happen.
I'm not sure if it is just Steam, since the same thing happened when downloading a driver from Geforce Experience, but when downloading a 1 GB test file from thinkbroadband.com no hanging occurs. I know Win10 just updated on me yesterday so I think that could be a suspect.
My system is plenty powerful and has never had a problem handling downloading (multiple files) and still playing games/streaming video. I could really use some help on this, it's the first time my system has run annoyingly slow since I built it a year and a half ago. Also, I have had programs running at 99% CPU before and never had such a slowdown like this and it isn't even reaching a full 99% now.
I've updated my ethernet driver, graphics driver, ran a ccleaner scan, ran an mbam and avast scan, reinstalled avast (lag happens without an antivirus too), have tried downloading to all of my separate disks and get the same slowdown. None of my hardware is showing as running at full capacity in performance monitor.