Choppy Video Playback of Purchased Content

So, recently built an HTPC with Windows 8.1 64bit. Using iTunes 12.1.2, all my video content purchased from the iTunes store is slightly choppy. It's as though it's skipping a frame or two a several times a second, and occasionally, once or twice per video it there will be a bigger more noticeable skip. It's especially distracting in any smooth camera movements, as they are smooth no more. This only happens with purchased iTunes content, other movies ripped from DVD's etc plays perfectly. The video's all played fine on my iMac, but I don't want to watch them on that.

Any remedies out there?