[CentOS] yum provides on centos 5.2

I am trying things like "yum provides alsamixer" on centox 5.2 i386 and 
x86_64
also "yum provides vi"
"yum provides gvimdiff"
"yum provides dumpiso"
"yum provides uname"

All of these return "no matches found"

is something broke???

These are just examples. I was trying to do "yum provides xf86Modes.h" 
it returns no matches also.

Jerry