I think the biggest problem here that Nobody has addressed yet is that SpikeHunter here is trying to install an outdated mod on a new version of Minecraft.
SDK Guns mod hasn't been updated since 1.3.2 and has an extensive list of dependencies.
In short: You can't have SDK guns mod. You're better off deleting the /bin folder and starting your minecraft.jar over from brand new.
Also-- akanton: You mean the META-INF folder..?
