The file does opening QT7 so one would assume it has the codec? why is it not converting when I start qt 10?
As previously mentioned, there are certain caveats for specific file container, compression format and operating system combinations. In fact, you have not even stated what "not converting" means here. (E.g., refuses to convert or goes through the conversion process but does not output playable content.) For instance, if you are really using Snow Leopard, then QT 7 (with the MPEG-2 codec installed) could open/play an MOV file containing MPEG-2/MP2 compressed data while the QT X player is not programmed recognize, play, or convert the same content. You would have similar problems with MPEG-2/AC3 VOB files in that they will open in QT 7 (but not play the audio) but could get QT X to correctly play them by simply changing the file extension. On the other hand, MOV files containing DTS audio may be supported by QT 7 (with Perian installed) while QT X would refuse to attempt files conversion (without Perian installed) but attempt file conversion (with Perian installed) and end up with an empty audio track.
What can I do to make it work, other than the external provider solution you mentioned?
You must determine the specific compression formats used in the MOV file. In turn, this would determine if or how the compression formats might be supported by QT X and/or to what extent. In some cases, if the MOV file is fully playback supported by QT 7, then it could (in most cases) be converted by upgrading the QT 7 player for QT 7 "Pro" use or use the free MPEG Streamclip download (which uses the system's QT 7 "Pro" codec configuration/conversion routines for conversion) to handle the file properly.
Since most users don't want to know/learn about the various potential codec problems involved in converting the various file type, compression formant, operating system, and QT version combinations, the use of a self-contained conversion app like HandBrake to turn your MOV files into H.264/AAC files (compatible with all current QT-based player and/or editor apps) is usually the easiest approach. If you still prefer to use QT X for conversion, then you will have to provide specific information regarding the compression formats in the various MOV files you wish to convert. (I.e., this information can be found in the QT 7 "Inspector" window.) As each combination of variables may require a different but specific QT solution, most users prefer to give up and try a more "universal" dedicated conversion app.