I've got 2 answers for you, well 3, but it all depends on how the drives have to be seen.
By seen, I mean when... by the BIOS and before W7 boots or after this by W7? Chicken and Egg sort of deal, which came first?
I've had RAID configurations on other systems, and for those, even though the BIOS is set to RAID, a RAID controller/driver is need so the BIOS can pass control to that to start the OS booting process. Generally this is h/w based, and before Windows start, it has to initialize the disks. When it is active, you get a screen of information or a set of keystrokes to use to get into it? Usually CTRL-I or CTRL-G is the keystroke set depending on what RAID controller you have. You didn't say if you saw this or not?
It also isn't clear if you already have W7 installed or not?
If you HAD W7 installed already, I don't think you can switch to RAID and have it boot? You need to do a clean install I would think?
In either case, if you just want to install a non-SIGNED digitally driver there are 2 ways to do it...
Boot using F8 and select the choice to not check drivers. This is temporary to install one. I've used it and it works. I've seen comments that this is only good for that boot and the driver wouldn't work on other boots unless you use F8 all the time, but that didn't seem to be the case for me, the driver installed and the device worked fine on normal boot.
A more 'permanent' solution can be found HERE.
If you've already installed W7 and now want to switch the disks to RAID and are using the Intel RAID, here is a LINK that details how to do it for Vista, but should work for W7 I would think?
Hope this helps,