Resetting Mouse?!

I've just set up a Mac Mini 1.66Ghz with OSX 10.4.5 for my folks. However, when I tried to double click folders on the desktop it wouldn't allow me to open them without going into the finder via the dock. I realised this was probably some setting in the system preferences, anyway in the mouse setting I inadvertently switched it to a right click button (the mouse is an old McCally one with one button) and now I can't get the thing to switch back as the click serves as a right click only. When I got home I looked at the settings on my own G5 running 10.4.7 and I don't even get the option of changing the button. Is that because the Mac Mini saw the third party mouse and thought that it may be equipped with a right click button? Is there a way to default the system settings back?

Any help would be greatly appreciated.

Thanks in advance.

Otis F

I'm sure that in System Preferences you should be able to customize the mouse settings.