[CentOS] Are these steps for re-installing Gnome correct/safe?

Perhaps I am not using the terms correctly then. By "return to default", 
what I mean is that the menu options that were available when I first 
installed CentOS be returned to the menu, the desktop theme be reset to 
the original, and the icons as well.

I'm not sure I understand how my current desktop can be considered to 
have successfully returned to it's "original" settings if it looks like 
the mess it's in after I've spent the last few weeks experimenting in 
installing themes.

Further, I discovered that a new problem has emerged. Every time I log 
out, before the log in screen comes up I get an error saying that the 
"current program can not be loaded. I will attempt to load another. I 
hit "Okay" (the only option), and it might do that a couple of times. 
And then eventually I get a log in screen. I tried using "switchdesk" to 
set the default login to Gnome, but that does not make this error 
message go away.

Dave