[CentOS] Update from 5.2 to 5.3 kernel not on mirror

> Interesting.....I thought that i686 used instructions only available 
> on later processors, i.e. i486 and pentium III do not have the later 
> instruction set to accept compiled code for i686.....
> I'm no expert, but that is why there are i386, i686 and x86_64 type 
> packages to cater for various processor types.

pentium-III is a i686, as is pretty much everything since Pentium Pro


i386 - 386
i486 - 486
i586 - pentium, pentium w/ mmx
i686 - pentium pro, p-II, p-III, p4, core/core2/etc.