I'm running Vista with a HP Pavilion Entertainment PC dv6000

Movie maker works fine, until I add a transition (I've only tried 2: Fade
and a different one that I can't remember), when the preview stops working,
the play button has no effect (it even stays as play, it doesn't change to
pause) and full screen mode has no effect whatsoever (ie it stays in normal
mode). As soon as it is deleted, it works fine. Sometimes if you're lucky, it
will let you show the video once, but then it will stutter like mad on the
transition and then go black and stop.

Even with transitions, however, exporting works absolutely fine, including
the transition and all.

I tried downloading WMM 2.6, but it won't import my project from the new
version and I don't want to make it all over again!

So, what I want to know is:
1) How can I get transitions working?
2) Failing that, how can I convert my project to a WMM 2.6 project?