I made a discovery today which early adopters of 64-bit Vista probably already knew about if they were using IE7. My excuse is I usually use Firefox, so it was a new problem to me. :)
It turns out that Adobe haven't put out a Flash plugin for 64-bit computing yet - so IE7 couldn't display videos for me.
Anyway, in case it helps anyone else, here's the problem and workaround!
I'm running Vista in 64-bit mode, and when I started using IE7, I couldn't get videos to display. Upon visiting the Adobe site to see if I needed to upgrade my Flash player, I found the culprit:
"Flash Player is not supported for playback in a 64-bit browser. However, you can run Flash Player in a 32-bit browser running on a 64-bit operating system."
After pausing for a moment to boggle at the fact that a plugin as ubiquitous as Flash isn't available for a 64-bit browser yet...
I consulted some friends (and friendly search engines) and while I could find a few workarounds for Adobe's lack of 64-bit browser support for Safari/Linux users, I didn't see anything helpful for IE/Vista.
Fortunately, a friend came to the rescue with a very easy solution. Turns out that Vista ships with both the 64-bit IE7 and 32-bit IE7. So I didn't even need to uninstall/reinstall anything - opening the Start bar showed me both versions of IE, so I just deleted the 64-bit version (which is pretty useless without Flash, I think) leaving the 32-bit version of IE as my default.