Just to be sure... have you made sure your browser and all it's supported technologies (.NET, Flash, Java, etc.) are up to date? You can test the plugins for Flash and Java at their respective websites as well, just to make sure something odd like a firewall isn't preventing the executables from running properly.

May need to update Windows Media Player as well, as it uses some of it's underlying support for media playback. Also, make sure that .NET 3.0 is enabled. It is not enabled by default in most stock installs of Windows 8 (not sure about Win7 now). It can be toggled by going into the Control Panel and looking under Programs and Features ->Turn Windows Features on/off. A lot of things were deprecated in the move to .NET 4, and it could be causing issues if you don't have .NET 3 activated. It has been known to even prevent some install programs from running properly.