I recently had a raid 0 setup that could boot on its own. In the bios it would be set as the only boot device and go fine. But recently something happened where I had to reformat everything. When I reinstalled windows, I found it very odd that I didn't need to load the raid driver in the installation, the raid 0 drive was already there from the get go straight from the boot from the dvd. The installation was fine and all goes well, but If I dont enable Raid 0 drive as primary boot and Single disk thats not part of the raid setup I will get this error Status: 0XC000000E The boot selection failed because a required device is inaccessible. I do not know how by just enabling one more boot device in the boot selection menu only stops this from happening. My computer is working well, but I'm just stumped how a drive not in the raid setup that is blank and formatted makes my computer boot into the raid whereas if the raid was the only boot device in the boot menu it goes to crap? any suggestion to the cause of it?
The root of this is where device drivers are stored, and when Windows loads them.
In your original system you were able to load Windows and run from the RAID0 array. You comment that you were surprised to see that you did NOT have to load the RAID driver with the "F6" key process when you re-installed Windows. Well, in fact, you should have. That step is necessary to add the RAID driver into the Windows package where it is installed so that it can access the RAID device to boot from. Without it, Windows has to load from a device it does understand and then look for a driver for new devices it can use.
Assuming you are using an on-board RAID management system in your mobo, that system allows you to examine all the hard drive units in the machine and assign two of them to a RAID0 array, then Partition and Format the array ready for an OS to use. All of that is done in the BIOS. Once done, the array will appear to any OS as a valid piece of hardware storage, but it still will need a driver to know exactly how to use it. In your case, all of that had been done already. So, when you started to re-install, that RAID0 array still existed as apiece of hardware that the Windows Install routine could recognize. However, it still could not use it with no driver installed.
So you did a new Install without loading a RAID driver. That means it could NOT install windows to the RAID0 array or boot from it afterward. It probably was installed to the non-RAID third hard drive. That is very likely where your machine boots from now. To verify, check the size of the C: drive in My Computer. Does its Total Space look like it is on the non-RAID third drive unit? Now, since the Install routine would have found a RAID array in place, it probably installed in itself a RAID driver so that it could use the array as a storage device.
Net result is that I expect that Windows is NOT anywhere on your RAID0 array - well, at least, there is no new re-install there. If you did not wipe the RAID0 array clean, it might have an old install there. But your system now must be booting from the other drive, because it has no RAID driver to use for booting from the RAID0 array. The only driver it can access on the new Windows Install is the built-in one for an IDE or a SATA (or AHCI) device. Only AFTER Windows has loaded from that device can it look around on that resource to find and load from there the driver that it needs to access the RAID0 array.
So you have a good system that boots from a non-RAID drive and then makes sure it can use the RAID0 array for storage. One advantage is that, even if your RAID0 array has a problem, you can still boot the machine.
If you really want to be booting from the RAID0 array, you will have to re-install Windows but be very sure that you do two things:
1. Use F6 to load the RAID drivers; and,
2. Specify that the installation must go to the RAID0 "drive". If you want to make this a nice clean job, disconnect the non-RAID drive first. Make sure the boot device is set in BIOS to be the RAID array. Re-connect the third drive only after Windows is running from the RAID0 array. At that point you could leave the third drive's contents untouched in case you ever want to re-adjust things and have it boot from that drive. But if you know you won't do that, then I'd suggest you copy all the useful data off the third drive and then Delete all its Partitions and Create and Format a new one to make it a completely blank new HDD.