Make sure you completely uncheck the box (not just change to a grey check mark), and make sure to apply to all subfolders as well. You may also need to have administrator priviledges if you're in Win2K/XP

Thank you. The box is completely unchecked, and I am applying it to all subfiles/folders. I have administrator privileges on the PC as well. Any other suggestions?

No Microsoft OS ever used the readonly attribute on directories for what it was meant to be used.
Back in the days of DOS, it wasn't used at all (DR-DOS et al used it though.)
Starting with Win95 MS used it as a flag for explorer to look for a desktop.ini file inside the dir.
Dosbox isn't using the readonly flag either, so that's not the reason for your problem.

There are a few things you can try:
- did you change to c: drive or are you trying to install from drive z:?
- can you copy something with explorer to c:\dosgames?
if you can't you have insufficient privileges (administrator doesn't have all privs - he can only get all.)
- type "dir" inside dosbox - do you see the copied files?
if not check your mount command.

Yes, to all your questions. I changed to the C drive and I can copy files using explorer, and dosbox sees them there. I do have to remount the drive first though.

In that case you should probably tell more about what you are trying to install and what errors occur. I don't think it has to do with readonly setting.