Set Launch Options...
The game may have defaulted to DirectX 8, causing portals to be rendered without effects. Add -dxlevel 90 to the game's launch options to run the game in DirectX 9, then remove it after running the game once or your in-game video options will keep resetting back to the defaults.
Before Portal 2 was announced, Valve ran an ARG that cryptically hinted at a sequel through an update in Portal. The update added a radio to find every single level, and carrying them all to the end to be vaporized caused them to emit shrieking noises. These noises could be decoded into pictures that seemed to hint at Portal 2, which was later confirmed. Since the ARG serves no purpose anymore, the audio that these radios play to alert you to their presence may be distracting. To mute these radios and achieve a near-vanilla Portal experience, follow these steps.