Some of my PC applications don't work anymore. Help?

I don't know what caused it but some of my applications don't work anymore, these include; Windows Media Center, Acer Empowering Technology, PSP Video 9, Pinnacle TV Center and ATI Catalyst Control Center: Monitoring Program. These are only a few of them. Empowering Technology and ATI Catalyst Control Center: Monitoring Program are startup programs for which I get an error message that gives me an error code. It says something like 'Fatal Error. Application will now terminate'. As for Pinnacle TV Center I get '.NET 2.0 Framework is not installed. Please install .NET 2.0 Framework. With PSP Video 9 and Windows Media Center they just won't launch. I am running an Acer Aspire 5103WLMI Laptop with Windows Vista. Any help will be greatly appreciated. Thanks in advance ;) Mike