Preview images (And a clip) from a lost "Valve Visit" video by VX Half-Life (Later HalfLife.org) on April 8th 1998, presumably showing much preview footage of Half-Life and other footage from behind Valve's closed doors.

Sources:

http://web.archive.org/web/20000815065639/http://www.halflife.org/files/multimedia/

> valvevisit.avi

> valve2.zip