Adobe Premiere Pro Preview Not Playing Full Speed
1. Corrupted Media

I'd bet you've got a problem with your media.

The hint is that Premier Pro auto-detects it at 10fps.

Premier Pro is broadcast production ready, so it's unlikely the cause.

You could try ffmpeg to give you an idea of what's wrong.

ffmpeg -v error -i file.avi -f null - 2>error.log

That will give you a log file of errors.

see https://superuser.com/questions/100288/how-can-i-check-the-integrity-of-a-video-file-avi-mpeg-mp4

2. Cache

Another thought is there may be cached media previews that are broken. So clean the media cache database and move it off your boot disk.  

3. Overclocking

I don't like overclocking a system until I know it's stable. That could be a problem there.

4. Windows version

You don't mention which version of Windows you're running (7-10?) I don't know anyone running production systems on 10. But that's not a lot of people.