I need help off the bat with Boot Camp

I'm running OSX 10.4.10 and every time I try and open Install Boot Camp Assistant.mpkg, I am told that the destination folder Boot Camp Assistant is on a locked volume and to try another one, then prompting me to pick a folder to open. When I do, it gives me Error #17530 - it specified a file and I gave it a folder. I am at a complete loss. What should I do?

I have the same issue, but even with other dmg files. My Stuffit expander opens and states "Error #17530 An error occurred attempting to expand 'Install ABC.pkg'. A folder was specified when a file was required.". I am stumped it used to install just fine before. What could I have done to lock folders or mess up the expanders preferences?

TIA