SteveM
Try this tool for converting your Quicktime files. It's FREEWARE.
MediaCoder download from
here.
Or
RAD Video Tools (video file converter) download from
here.
I think the double speed problem seems like a Codec problem. You can also try downloading and installing the
SLD Codec Pack 2.2 from
here. See if that helps solve your problem.
This codec pack also has Windows Media Classic. I agree with Iridium - Windows Media Player is very bloated and waste of resources. I use Media Player classic all the time as it loads a lot faster and players my videos faster and easier to fast forward, rewind etc....