Vista - Vista extremely slow/freezing and Aero dissapeared after reboot

I rebooted my computer recently and when it started up, the Windows Classic theme was enabled, and all options to enable Aero had disappeared.

In addition, everything in Windows Explorer is incredibly slow, most notably opening folders on the start menu (it freezes explorer.exe for about 45 seconds then closes the start menu; when i try again it works for that folder only. Everything else freezes and repeats the process.) I also noticed that none of the services show up in the Service management window.

Any idea what this might be? The only thing I installed recently was Visual Studio 2005, with all updates and the service pack. Oh, and I tried System Restore.

I just got this computer a month ago and I finally customized it with all of my programs and settings. I really don't want to have to fully restore it.