Portal 2 walkthrough part 1...

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MP4 (Source) 1280 x 720 125.72 MB
FLV (Flash) 640 x 360 50.4 MB
FLV (FlashHD) 1280 x 720 87.78 MB
MP4 (480p) 640 x 360 30.28 MB
MP4 (720p) 1280 x 720 91.73 MB