Unable to install programs in Tiger

[appaloosa]

I recently upgraded from OS9 to OSX.4 and after installing Tiger I tried to install a few programs that I had downloaded, and one on disk, and none of them would work. I am trying to install office for mac, and stuffit, and when I click on the files, I get an error messages saying: 1. unable to unarchive into desktop error 1 - operation not permitted, and 2. Quicktime cannot open the file, it is not a file that quicktime understands.
Why would quicktime be the program to associate with an installer anyway?

Has anyone else had this problem? I've tried to change what program opns these files, but it doesn't work. I just can't figure it out.