thanks for migrating this post to superuser.com.
to answer to my own question. iI just found out that win7Windows 7 x86 guest in kvm with -soundhw ac97 can have sound. iI guess we really do not have a driver for that kvm virtual audio device in win7Windows 7 amd64. so, iI think this is as far as iI can go. win7Windows 7 amd64 guest in kvm is DEAF...