Yeah, I know, I wrote the included undat tool, just forgot that DAT explorer can't handle FO1 DATs. Try: https://fodev.net/files/mirrors/teamx-utils/DatManL1.2.rar or https://fodev.net/files/mirrors/teamx-utils/F1DatExplorer0.3.rar or as Wipe mentioned, dat2.exe by Anchorite that's included.