Problems with video preview or launch

[Kevro]

Hi,
seem to have developed a problem with my LW in the video library previewing or launching a video.(music is no problem). If I attempt to launch a video one of three things could happen.

1/ Nothing happens (thats the good outcome)
2/ LW shuts down
3/ Whole computer shuts down and restarts.

Options 2 & 3 are more likely to occur if I double click or on the third attempt.

Up until a few days ago everything worked fine.

Coincedently, a problem that is I suspect is linked has occured when launching video or music from my shared file direct. When I double click or left click-open the following error message occurs

"This file does not have a program associated with it for performing this action. Create an association in the folder options control panel."

If I left click-play it works fine. I have been to the control panel-folder options area and could not sort it out. That is probably because I have very little idea of what I am doing. I am using Windows XP and have plenty of available memory 56GB.

Hope U can help
Kevro :