My computer has Windows 7, and I'm pretty sure it's not something to do with the browser (Mozilla Firefox updated to at least v6, I believe). It would save my files into my downloads folder, and when I'd try to open it, the screen that would normally say "Run program" or "Save file" never pops up. I've tried opening the task manager to see if it was one of the processes (I'm not sure if it would show up at all, even if it worked) and it never showed up. I also have problems with my computer recognizing things that I plug in, like flash drives and cameras. I usually have to manually open them from the Computers folder. If you can tell me what's wrong and how to fix it, it would be much appreciated. Thanks.

Just reinstall your windows and then try. Also confirm your ISP that there is no problem on his side.