You do not need MP10, MP9 is fine.
As far as the missing transitions go it depends on what version of Movie
Maker you are running.
If it is version 1.0 or 2.0 you can simply reinstall the program and that
should fix things or you can upgrade to version 2.1 by downloading SP2 from
Microsoft Update.
If you are running 2.1 already the problem is a little more difficult to
fix.
Reinstalling can still be done but you need to uninstall SP2 and then run
Windows Update to reinstall SP2 since Movie Maker is integrated into the
Service Pack.
A better choice would be to try using System Restore back to a point where
the program was working.
An even better choice would be to try to reregister the DLL files but I, and
I really need to write this down next time it is posted, can't remember the
command to type in to do that.
-Wojo