Hi,
self reply, if someone is interested...
It was very easier than expected:
- put some hd on the SB750 set as RAID
- put the initial hd on the SB750 number 4 connector set as IDE
- put from there (if there is some problem booting, use something like super grub 2 boot disk, e.g. I have a grub 2 installation on that hd and grub refused to boot)
- make the window installation recognizes the new hd as a standalone SB750 RAID disk (you may need to manually install the driver from the windows 7 installation SB750V set)
- done