Welcome to Easypano forum. We seldom have preview problem. Please check whether you have Flash player installed. If you have Flash player but still could not preview the tour, please send me your tour project and I will test it on my side. Tour ptoject file include a folder (with all the resources in the tour) and a .tw file.
I tried to reply to your message in private messenger, I don't know whether you have got my reply. Please send me your project file and I will test on our computers with the same OS. Upload the project files here: http://www.mediafire.com
Is there any error message when previewing the tour? What does the previewing window look like, can you send me a screenshot?
I have the same issue on my laptop running WinXP with TW6 and the latest version of Flash. I don't use my laptop very much so for me it is no big deal. I just publish the tour and watch the tour from the published files as my preview on my laptop. TW6 on my main production computer works fine (as far as the preview goes)