Creative Zen Vision Videos

Newbie here..

Recently purchased a Creative Zen Vision and according to their site it can accept MPEG4-SP videos. My friend shared her video from iPOD which was already in MPEG4 version. When I was loading it to my CZV, it prompts me to convert the file first.. What's the difference between MPEG4 and MPEG4-SP?

Anyway, CZV comes with a Creative Video Converter so I can convert those MPEG4 to a file usable by CZV. The final output is WMV and is considerably smaller in file size. But the conversion of a 50 minute clip takes almost 2 hours! Is there any freeware I can get that converts videos faster?

Lastly, what's the best file format that's small in file size but can still maintain the quality of the video?

Any help would be highly appreciated! Thanks in advance!