Yes it can be done.
(the motherboard is a 945GNT with ich7)
We are trying to convert a Raid 0 (2x80Gb HDDs) to a Raid 5 by adding another hdd (a 500Gb hdd we had lying around) and then using the RST migrate to raid 5 feature. However, when we try to change the raid type and select the third disk, hit ok, it sits there for about 30 seconds timing out before reporting that an "unknown error" has occurred.
Is it actually possible to convert a striped raid 80Gbx2 to a 3 disk Raid 5 array? Is that what the problem is here? (all drivers and bios etc., are up to date)