After installing Vista I found that IE7 would not show Flash content. Instead, the page I was trying to view would tell me that I needed to install the latest Flash Player (example sites: Google Finance & YouTube). Clicking on the given link, I found myself at Adobe's site where I would successfully install the latest player. After successfully installing, I would navigate back to the original page where that had Flash content but I would still see the error message stating that I did not have the latest Flash Player. Even after rebooting, the error message would not go away nor would the page display the Flash content.
Googling for this problem at first turned up nothing. People who complained about this were shot down by other users stating things such as "you need to enable Flash content" or "you need to enable javascript" as fixes, which I'm sure was followed by a big "DUH" and ignored from there on out. Like myself, people having these problems checked all of these settings and indeed all were correct but embedded Flash content would still not play. These statements usually fell on deaf ears. That is until I ran across this post on Channel 9.
The post claimed that to fix the problem all that was needed was to run the following:
C:\windows\system32\Macromed\Flash\FlashUtil9b.exe
Yes, this solved the problem but the poster (joem83) did not elaborate as to why this works but stated simply that "Flash for Vista is still in Beta". So, if you are currently having Flash problems with IE7 on Vista, run FlashUtil9b.exe to correct the problem. It works.