Jorabi, the Intel® Rapid Storage Technology does not have a rebuilt option out of the operating system.
Was the operating system installed on another hard drive or it is part of the RAID5?
If the OS was installed separately from the array, you can do a clean installation of the OS and then once you install the RST, you can rebuild the RAID.
If the OS was on the array, you can try to do the same, but once you access to the RAID, I would recommend you to back up all the information and then recreate the array.
At this point we cannot assure you these two options are going to work. There is a 50/50 chance the RAID could be rebuilt without problems.
Another Software named Intel® Embedded Server RAID Technology II, allows customers rebuild an array without accessing the OS, but this SW is for server systems only. For additional information you can check the following link http://www.intel.com/support/motherboards/server/sb/cs-032032.htm