Pixelated Slow motion/regular video

When I take footage from my iPhone 5s and transfer it to my Windows 8.1 PC, it's pixelated and saturated. I'm trying to take a video I captured on my phone and transfer it to my PC and when I open it, it's a big low quality, pixelated mess. I've tried email and plugging it through the usb and nothing helps. Please help! Thank you!