HaloMods "Classic" Read-only Archive

Hello,I am a newbie here and I have wanted to edit the current HALOPC warthog skin,I have used paint shop pro to make it and then made it a dds file but it doesn't seem to work,it says it is small that the existing data (even though in the map tool I clicked the image to show it full) and then when I click continue it says somethin like an unhandled expection has occured in your application,and at the bottom says "Unable to read beyong the end of the stream" can anyone help?

Okay I fixed that problem..now HMT is telling me that the image I am trying to inject is small that the existing data,how can that be if I took it from the full size picture....I mean geez I saved the texture and edited and such,so it should be the exact same..then it says the image must be injected at DXT2 or DXT3...what do I do now?