How to detect if user has already seen the page - help

In the home page (index.html) i have a flash intro. The first time a user sees the website, the intro should play. Once he goes to another page (about_us or contact_us) and comes back to the home page, it should show a different swf (the version without the intro) - i have created two swf files. I need to know how to change them when the user has already seen the intro or was in the home page before. When i googled, i found something on cookies. I have no clue on how to set them and change the swf file. Would be great if someone has already done this or point me to a tutorial.

Please Help.

Thanks.