HaloMods "Classic" Read-only Archive

I've downloaded hmt a couple of times, and it doesn't work when I try to open it. I have used winrar on it, so it's not that. It tells me that I need a specific version of .Net Framework. I have .Net Framework already, but it says it can't detect it...

which site...? And what's hmt? (Like I said... My brain doesn't work sometimes...)

Uhh, first of all, I'm a dumbass. Just thought I'd get that cleared up. Second of all, where the hell do I get the .dds files? Third, I don't think I have photoshop, do I have to buy it, or is there a free download somewhere? Thanks!