Remember I provided the download link for flash player 10 for Vista, seems like there is an issue of flash player on Windows Vista. Once you have finished downloading it or upgrading the flash player plugin, you will not be able to play or watch online videos easily with this new version.
Usually the problem is found when you are updating from Flash player 9 to Flash player 10. Though I am not sure if this has to deal with the Windows Vista bit (32 or 64 bit Vista) but here is an easy solution, perhaps the best fix that will definitely work for all the people who are wondering why they can’t watch YouTube videos on Vista.
All you have to do is run the Flash debugger on Vista. Flash debugger is a standalone 2mb program which will check for vulnerabilities and fix errors that are associated with Flash player 10.
Download Flash debugger exe file and run it on your vista system. Restart the browser once again and the flash player 10 will work now! It works perfectly, hope this fixes the issue.