Fuji Finepix A820 camera. Videos and Photos are not all viewable on PC

When I look at pictures or video clips on the camera screen I can see them ok.
When I try to look at them on my PC (via the sd card) I can see some pictures, but some cannot be displayed (same for some videos). PC has windows XP

If I put the sd card in my Wii, I can see some of the pictures which weren't visible on the PC, but not all of them!

I've tried installing the fuji photo software on my PC and downloading latest update from fuji but still no joy.

any ideas?