AACK! DISASTER!! WHAT DID I DO!?

More importantly, how do I Un-Do it!

I was working on the Mac, had my Finder open and I must have clicked on the Mac HD icon w/o realizing it and dragged it off the viewer window. I released the mouse, saw the puff of smoke, had to figure out what I'd done. Anyway, the HD icon was gone.

I kinda freaked, but just clicked on the icon on my desktop, made an alias and dragged it into the first column of the view window.

I had to restart my Mac for something else, and when I did it came up as completely new. My desktop files are all still there--I need to go in and see if my programs are, but when I open Mail, it acts as a first-time use. My settings for internet access have all disappeared, bookmarks, desktop pics, dock reverted to original etc. I had to go into one of the other user accounts to be able to get online to post here.

So, anyone know what I did and how I undo it?

Thanks

Jeri