I eventually, in desperation, tried the XP version of the RAID/SATA drivers and bugger me they worked! Once up and running I then used the device manager to install the actual 'vista' drivers but got a blue screen on boot up. I might give it another try during the next two weeks - if there's no driver support improvement by then I'll stick with Vista x86 and wait another year until there are more mature / versatile LINUX versions available out there. That's very basic / essential stuff! I didn't expect to run into any such show-stoppers with Win7 RC 圆4, decided to use it from now on and then buy the "Ultimate" version immediately upon availability, but under said prohibitive circumstances this isn't a good idea. My hardware: ASUS M3A 78 Pro AMD Phenom x4 8850 BE 3.0 GHz 4 GB RAM (DDR-2 800 MHz CL5) 4 SATA HDD's (single drives, no RAID) 2 SATA optical drives (DVD ROM/RAM) ASUS/ATI EAH3450 Graphics Onboard Graphics enabled with "Hybrid Crossfire" It is a pity that there are not even Win7 OEM mobo maker drivers available yet for the AMD SB/NB chipset integrated storage controllers. There might be a slim chance to get AHCI / RAID up and running by activating Microsoft's generic Msahci driver subsequently (after IDE install) via registry tweak and then boot in AHCI mode, but I haven't tried this yet. In due course, the only way to go is to install Win7 RC 圆4 in IDE mode - no AHCI, no RAID.
This happens with the latest ASUS and AMD/ATI 圆4 drivers - they're obviously "unsigend" to Win7 圆4, but work flawlessly with Vista x86 and 圆4. However, at 1st reboot in AHCI mode it stops with an error message indicatng that it couldn't load "unsigned drivers".
After that, it displays and loads the drivers of your choice - eg Vista 圆4 AHCI/RAID (AMD) drivers and resumes the installation process. Ross, the Win7 RC 圆4 ("clean") install setup process does recognise all drivers offered via diskette, USB-stick or CD-ROM if you un-tick the box "search for signed drivers only" on the 3rd-party driver installation selection page.