Hi! Finally i have solved the problem with partitioning, and now i am setting up NS7. Got some problems on that HP server when i choose manual partitioning - i haven't created /BOOTBIOS or /BIOSBOOT partition but after some struggling NS7 as host system works just fine.
I had also some problems with Virtual Machines app (webgui) but it also is now ok. I just found a "small" bug in the wiki(https://wiki.nethserver.org/doku.php?id=ns_webvirtmgr) regarding creation of ISO folder which is: after manual creation of ISO folder and then setting it up via WebGUI it should be started (which was not in my configuration - can anyone could check it please if this is problem with my setup or it's the right behavior).
Another info - for installing MS Windows Server 2008 R2 don't check VirtIO while creating New Instance - i was not able to add virtio drivers for that - there was strange error from MS Windows Server setup, but after unchecking it everything goes smooth