At first, I wanted to post a question, but I've found the solution.
 
Problem :
Windows (10) was installed first into a boot drive and runs fine.
 
Later, I adds 2 drives as raid setup (for my case, raid 0).
 
You'll probably boot to the bios and change SATA mode as RAID to enable further configuration.
- reboot - configure RAID via bios (for my case, ctrl + i, Intel Raid setup)
- then reboot back to Windows to finish up adding the new raid volume via Windows Disk Manager.
 
However Windows won't start - due do not recognizing your first boot drive - it has changed as RAID disk due to changing SATA as RAID mode - even thought it is not part of the raid volume you've setup for the other drives.
 
Here's the link to the solution. I'm using the alternative method at the bottom of the page via msconfig (boot to safe mode). 
 
http://www.askvg.com/how-to-change-sata-hard-disk-mode-from-ide-to-ahci-raid-in-bios-after-installing-windows/
 
After running through the steps, I'm able to resume normal Windows booting and managed to add / format the new raid volume via Disk Manager. At this point, I've still not installed any drivers, especially Intel raid utils, so I'm not sure if those are needed, or I'll run into any problem later. I've only verified it's working by copying some files to the new raid volume.
 
My setup :
1x Samsung Evo 850 120GB Os/boot drive
2x Samsung Evo 850 500GB for the rest (program, data, samples, etc)

Here's the alternative method in case the link won't work in future..
 
You can also try following method suggested by one of our readers:
1. Open RUN dialog box by pressing WIN+R keys together and then type msconfig (Windows 8 or later users can open RUN dialog box by right-clicking far left-bottom corner of desktop, then selecting Run option).
2. Click on Boot tab, enable Safe boot checkbox, apply the changes and restart your computer.
3. Upon restart, get into BIOS settings (by pressing DEL or F2 key most likely), change the hard disk mode to AHCI, might also have to change boot order SCSI, save settings on exit and reboot. Windows will now boot in safe mode.
4. Run msconfig again, go to Boot tab, unmark Safe boot option and restart PC.
That's it. Now your PC will work fine.
 

Anyone using Windows Storage Spaces instead of RAID?
http://windows.microsoft.com/en-us/windows-10/storage-spaces-windows-10