How to improve video playback on laptop?

Hello, my video footage from a gopro hero 3 plus is playing back very choppy and slow on my laptop, using real player and it is even worse in Sony Vegas pro. My laptop specs are 8 gb ram with a quad core Intel I 7 3630 cpu and a Nvidia 650 with 2 gb ram. I would think these specs are good enough even for gopro footage.

What can I do? I know little about computers so please bare with me. Will it help if I store the footage on an e ternal hard drive instead of c drive? Do I have to convert the footage to a different codec or format? Should I check anything else on my computer settings? All other videos play back very well.

Thanks

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