The safest way to save a movie from a Macintosh computer that you want to transfer to a PC is to save it as an AVI file. The problem is (as pointed out in the comments below!) is that the latest version of Quicktime cannot save AVI’s. To save an AVI file you’ll need to use Quicktime 7, AND you’ll need to upgrade it to quicktime pro which you can do here for US$30.
The older Windows movie maker (the one that came with Windows XP and Vista) only imports .asf, .avi and .wmv files. So if you want to export movies from your Mac that someone in the PC world is to be able to read, and better yet, edit, it will need to be in one of these three formats. QuickTime can export an AVI movie, but not the other two formats.
For newer PC’s, the latest Windows Live movie maker (included with Windows 7) can read QuickTime movies which is great. It cannot however save AVI files! (Only WMV). I assume this means that Microsoft is phasing out AVI files?
Anyway, for the present time AVI seems to be the best way to transfer files to a PC. It doesn’t where the file was created, iMovie, iDVD, digital camera footage or whatever. This is irrelevant. If you export it as AVI then a Windows computer can read it.
To export a QuickTime movie as an AVI movie:
1. In QuickTime 7 Pro select File > Export.
2. On the Export: list select AVI
Lastly, click the save button and it will save your movie as an AVI file that any PC computer can read.