[libvirt] building libvirtd fails on libxml-2

I'm running on Centos5.3 Building using: ./autogen.sh --prefix=/usr configure fails with checking libxml2 xml2-config >= 2.6.0 ... configure: error: Could not find libxml2 anywhere (see config.log for details). but rpm -qa | grep libxml2 libxml2-python-2.6.26-2.1.2.7 libxml2-2.6.26-2.1.2.7 libxml2-2.6.26-2.1.2.7 So what's the problem, or better yet, how to fix it? Thanks, Dan