Vista wont install on Sata

Sorry to post this in two places but Im going absolutely nuts here. (mods feel free to delete my post in the OS area)
Im trying to install Vista Ultimate 64 on a raid 0 array, but everytime I get to the screen that lets me select where I want to install, windows says it cant find a compatible system volume.
I set up my raid in the Bios and there dont seem to be any problems there, it is recognized as a raid array by the system.
When I get to the selection screen in Windows, windows shows it as one drive which Im presuming it should do and it recognizes my other sata drive correctly too.
Since my motherboard didnt come with Vista drivers I have downloaded the latest ones from both Asus and Nvidia for the chipset that controls my raid and Sata devices and put them on a floppy. When I click on load drivers in the menu, it recognizes and installs them without any problems.
After installing the drivers I click on next and I get the message that Windows cant find a compatible system volume. Even when I try and install on my no raided Sata drive I get the same message.
I have installed both the raid dirvers and sata drivers for the chipset but it just wont recognize any of my drives.
Any ideas?

My system is as follows
Asus KFN5-D SLI motherboard with Nvidia Nforce professional 3000 (mcp55) chipset
2x Opeteron 2212 processors
2 gig ec reg mem (had 4 gig but the install kept crashing)
2x WD raptor 36 gig (set up in raid 0)
1x WD raptor 150 gig
1x Optiarc DVD (sata)

Thanks

I finally got it to install! After many many attempts all with the same result, I was about to give up when I decided to try and install it without activating it first, incase vista was getting confused by the serial key. I selected the correct version from the list and it st installed without a problem, weird. Anyone have any idea why this would have made the difference between vista being unable to find "a system volume that meets its criteria for installation" and installing without a second thought?:confused:

thats a weird one, cant see why activation would cause a prob, it doesnt activate till after u build even if u check this box, well it does on my build anyway

btw the 4GB prob is known, simply stick the other 2GB in after install and it will be fine. Ive built a few Vista machines recently, some like 4GB during install others dont, cant see an obvious pattern