As Neven says, it is possible to have the bootable drive in the Raid volume but you need to check the compatibility on the motherboard for RAID capability.
Answering to your question, yes, It is possible to create a RAID 5 but It looks the problem may be caused by another component.
I wasnt actually looking for an answer to my specific issue in this post since I have sought help for that on another thread. I was just looking for clarification on the comments in the Microsoft technet article. I am sure myself that its possible to have any type of RAID as the boot volume since say with a hardware RAID the OS would never see the different drives as separate hardware. However since its posted on a microsoft site as a "fact" and its also referenced elsewhere, its used( cited) as a means to avoid providing support by HP in my case. Thats why I wanted a specific official Intel contradiction.
It may very well be that Micreosoft products are not capable of having a RAID 5 array as the boot volume, but the comments are over reaching IMHO to not clarify that?.
Yes in my specific case I believe its either a firmware issue or some hardware issue, but its hard to prove when you're running a "unsupported configuration".