How do I Compress a video file?

I have a ten minute video file that I need to compress and convert in order to edit it in windows movie maker. I have been searching and searching the web for hours on end trying every program out there and still nothing has worked. I need help! I need to compress the file so I can convert it using Zamzar because it says the file is to big. But I don't know how, It is a MOV file that plays in quick time. I need to be able to convert it to WMV or something. Please help! The file is 1.86 GB. I have no idea why it is that big but I need to make it smaller.