In reply to Sl@te Head:
easy tiger... I totally understand your points about support the artist, however the legal landscape regarding copywriter infringement isn't always as understanding. A pal of mine did a video on a ski/boarding trip of us all singing the bits of a chart topping pop song whilst doing daft things. he got a letter from the record company saying that "the band love your video, but..." he had to take it down.
anyway, the pixels in the video are very likely caused by the export getting confused about the fast movement on the screen of the paddle. can you try exporting it again, but either with a different output format or with less compression? you might end up with a larger file, but hopefully without the software getting confused as to where the big orange paddle has moved to.
I'm sorry I don't have movie maker so I can't tell you exactly how to do this... hopefully someone else (or the internet) can help further?