I was trying to clean up my system registry after malware changed some of the settings, and I think I inadvertently removed or changed the part that automatically executes explorer.exe on startup. Now, my computer will only boot up part way – the desktop doesn't appear. I can manually execute explorer and it will finish activating the desktop, but I'd like to fix it correctly. Is there a way to easily add this command back into the registry, and if so, how and where? If not, is there a download that I can use to restore the default settings for the system registry?