(Hi, new to this board! )

Why has everyone assumed that the C4 was placed there by DHARMA? The C4 looked to me to have been added long after the station was built, probably by the Others/Hostiles.

Why the assumption that Locke blew up the station? The Doc told Locke to enter 77 if the hostiles were overrunning the station, so perhaps 77 was a call for help. I think the others pushed the button destroying the C4 and with it the station. Either Mrs. Klugh or the russian could have called the others. Klugh from the basement before she was found, and the russian while Locke was playing chess...