I would recommend updating to Windows 10. I did a couple of years ago and saw an immediate boost in performance. My live key rig is on a laptop and the load times with Windows 10 are measurably faster. I posted about it on HC and I think it was flagged as spam or something and taken down. Total BS. It was easy and free to do the update, but that was years ago. Anyway. . .
I've never worked with Reaper. I know in Studio One or Sonar Home Studio with using a Tascam 1641 midi/audio interface, I've never run into many problems. From my experience midi/audio interfaces can be really flaky. I've gone through probably 3-4 different interfaces that never worked right, and banged my head against the wall trying to figure out if it was my controller or software, then finally just went back to the Tascam 1641 and everything works perfectly. I've tried other interfaces and I've not found one that works as well. I have three Tascam 1641's. You can get them on Ebay for a couple 100$.