I really like that QuickTime can easily and quickly record screencasts. But can someone please explain how I can save or export the resulting video in a format that will be playable on Windows natively? By natively I mean with no QuickTime, and no extra codecs etc.
The files should play "natively" in any Windows media player that "natively" supports standard MPEG-4/AVC video such as VLC. MPEG-4/AVC (H.264) video is most commonly wrapped in an MP4, M4V, or MOV file container. Since H.264 (MPEG-4/AVC) is the default video codec used by Apple (and most third-party) screen recording apps, if you want the finished content in a different compression format and/or file container, you will have to convert the screen recording yourself after capture.
So actually all I want to do is be able to export a format that is the most comptaible across all platforms.
Good luck! Unfortunately, you will always find a number users who have differing ideas regarding what constitutes the "best" compression format for this "cross platform" compatibility. (I personally am quite satisfied with MPEG-4/AVC since it is also used as a basis for Blu-ray and AVCHD content as well.)
The options in the export confuse me a little: "Movie", "480p", "720p", "iPod Touch & iPhone 3GS", "iPad, iPhone 4 & Apple TV". But on experimenting they all seem to export to .mov, and when I check that file format in my Windows XP install, it's not recognised.
With the exception of the "Movie" option which, if the original video and/or audio compression format are already QT compatible, can perform a "Save as..." action which merely copies the original audio and/or video data to an MOV file container, unlike all other options that convert the video to H.264 (MPEG-4/AVC). Also, you must have skipped testing all of the device targeted/iTunes managed formats which end up in M4V file containers. With regard to your "recognition" problem, what player were you using and did you also test the files with the extension manually changed to MP4?
Is there a way to export to avi?
AVI is a file container—not a compression format. If you want to create an AVI file containg a specific compression format, you will have to use additional software to convert the content. In many cases, the target format will likely limit your choice application. For instance, VisualHub (or MPEG Streamclip with a DivX component installed) can create a DivX/MP3 AVI file. QT 7 Pro or MPEG Streamclip can create AVI files using DV, DVCPRO, Motion JPEG, or Cinepak compression. Commercial converters may offer many other options. Your main problem here is that AVI is a legacy file container and most of the legacy codec components were turned off under Lion and remain off under Mountain Lion unless you've turned them back on.
Failing that is there any other free or open source software that can be used to achieve this? I just need something really simple/easy.
There are many options out there. For instance, does your "native" media player play H.264 (MPEG-4/AVC) content in an MKV (more modern than AVI) file container? If so, you could try the free HandBrake app to convert your screen recodings. As I had not previously tried this option, I created and posted an MKV anamorphic 2048x1440 (2560x1440) H.264 test sample file captured on my system. You can try downloading and testing it under your Windows OS.
http://downloads.walker4.me/downloads/Temporary_files/ScreenTest.mkv