Quicktime plugin? question

Hi all,
I am new to this forum and just beginning to learn multimedia web production. I am not a 'coder' so am using a very old version of GoLive, 4.0. I am putting together a multimedia presentation (volunteer basis) for a non profit organization that helps people whose lives have been affected by cancer.
I am producing and saving the quicktime movies in Final Cut Express, which is a software that I am also just learning (have done many things with Apple's iMovie). I personally am using a mac power pc. I have sent a link to my presentation, which currently resides on my webserver, to several pc users at this organization and they cannot view the movie but can hear the music. They get the same quicktime error message I get when I try to preview the movie in GoLive 4.0 "Quicktime is missing software to perform this operation. Unfortunately it is not on the quicktime server." On the html pages the movies seem to play fine and stream well on mac computers. On their pc's and the one that I have access to, the same thing is happening, a white box where the movie is supposed to play but sound does come through (same thing happens when I try to preview movie in GoLive 4.0)
Is there anyone out there that recognizes this problem? Could it be that GoLive 4 is coding or configuring an older quicktime plugin? I would really like to solve this and get the product to them as soon as possible.
Thanks in advance for any input.

Dennis