@Tommy8, you can go to the GIMP repository and get the dds plug in.
@Nuncio, you wont be able to open any that are encrypted, that resided in the standalone builds.
Is that the case with you?
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit