Why not F6 for RAID?

Okay I will try to keep this as short as I can.

First some details:
Running a RAID 0 (2x250GB) configuration through my nForce 4 (nVidia RAID).

I signed up for the Beta 2 version of Vista. Since my Opteron can handle
x64, I was willing to try this. I am currently running Windows XP 32-bit, so
I won't be able to install Vista from XP on a clean partition.

So I downloaded the ISO and burned it on an empty DVD. Then rebooted and
watch Vista to load... Then I suddenly get a message with "No disks found" or
something very similar. Okay, I understand it doesn't see my RAID 0
configuration, like all the previous Windows installments. So I rebooted
again and tried the old F6 key thing, so I could load up the corresponding
RAID 0 drivers. But to my surprise it seems Microsoft seem to have removed
that option totally?

Meaning I can't install Windows Vista X64; I am not presented in any way to
load my RAID drivers for Vista. Not with F6 and not with a menu during
installation. Also I can't do the workaround by installing Vista X64 through
Windows XP, cause my XP version is 32-bit.

Does anyone, in particular Microsoft, knows a way, how I DO can install
Vista X64 version through a boot with the Vista DVD?

Currently I am downloading the 32-bit version of Vista, which means another
whopping ~3 GB wasted.

My advice:
Please put back the F6 option during install, so you can select RAID (or
other storage) device drivers. Cause otherwise I won't be seeing myself
upgrading to Vista by 2007.

Again I want to point out, that I am not able to install Vista X64 on a RAID
0 configuration by booting it from DVD!