Establishing a software RAID5 with Diskpart seems to take DAYS with no end in sight - what gives?

I'm playing around with Server 2008 on a box that previously had a 8 disk x 500GB software RAID5 configured under Linux (Linux was installed on a USB Flash stick). 
Well aware that I cannot install Server 2008 on a Flash stick, I installed Server 2008 on disk 0, leaving disks 1 through 7 for the software RAID5.

I configured the RAID5 via Diskpart, everything SEEMED to go well but:
When I type "LIST VOLUME", the RAID5 volume continues to show its status as "REBUILD" not as "HEALTHY".
It has been like that for days now.
While I understand that initializing a 3TB-size RAID5 array may take a few hours, or even a night, or even a day (as in: 24 hours), LIST VOLUME continues to show "REBUILD" after several days now.

Is there some guideline as to how long it is supposed to take?
For instance, "allow 10 hours per terabyte" would be a great guidance.
Or: "Multiply the number of physical disks by the number of terabytes and the resulting number is the number of days it will approximately take".
By the way, the eight disks (seven in the RAID5) are normal WD 500GB SATA disks.
All the while, the CPU load on the server is 0%, which begs the question: Is the RAID5 creation going on at all?