今天下了个pidgin的安装包，结果需要安装gtk2.0软件包，从add/remove software 进入速度狂慢，估计是系统没有从cdrom而是从http上当软件包的，搞了半天终于发现可以更改的地方
move all files in /etc/yum.repos.d directory to a new file dircecotry (as /ect/yum.repos.d/tmp/)
except Fedora-install-media.repo
and change the baseurl variable in it to the cdrom mounted point
