For Vista, you can either:

IMPORTANT NOTE for installing vista over iSCSI:

The installation process is the same as windows 2008. But BE SURE to use the installation media with at least service pack 1 patched. The original CD without service pack won't find the iSCSI disk. Even if you succeed starting the installation with some trick for the original installation meida, For example, booting the PE by using the windows 2008 CD. You won't succeed either. The reason for this is: the setup program in the original media wouldn't install the NIC driver after copying the file. Thus results a partial installed but unbootable vista. Everytime you try to start it, You'll see BSoD.