[CentOS] Switch from SL -> Centos

[Nicolas Ross]

> The above would only update a package if the centos repos had a higher
> version number than the installed SL one.... I would strongly suggest
> something akin to yum reinstall \* and leave it to chug away (backups
> first naturally) for a while to refresh all the packages and teh rpm
> database to be in sync with the centos build..... requires matching,
> same build options for sure etc etc....
>
> In the event something crops up it at least eliminates an odd untested
> mix for certain fundamental packages like glibc etc....

Yes, I know, for that machine, it's just a desktop that has x-window, gnome 
and a console opened up all day. I don't mind it if it function strangly... 
In any event, I'll just wipe the whole thing...