Which motherboard / raid controllers did you move it over and what was the procedure?
Originally assembled on an Asus p5e-vm hdmi (ICH9R), moved to P5Q premium (ICH10R), then ECS GF8100VM-M5 (NVIDIA MCP78V), finally Gigabyte's X58 UD5 (also ich10r iirc).
Four disks, no hot spares, assembled under ubuntu 8.04 using mdadm. There's a wiki page on this for most operating systems, I used a generic one. Or man mdadm is also good.
Moving it over featured unplugging the drives, plugging them into the new board in arbitrary order, then running mdadm --assemble --disks=4 --uuid=xxx /dev/md0 && mount /dev/md0 /mnt/data. Doubtless I've got the commands slightly off, I don't have mdadm installed at present. It was consistently a single line, then mount though. I ran it with 3 out of 4 disks for ages too, excellent system. Doesn't need any particular hardware. It does however need you to run some varient of unix, and uses the cpu for parity calculations.
Decreased performance relative to a raid card is well worth it considering that a dead motherboard doesn't cost you all your data, but a dead card may well do. I'm more than happy to dig out my notes on it if you're interested (and not running windows, which I know nothing about).
Windows cannot boot from software raid.
Fail by windows then. I suppose I'm not surprised. Thanks for the link.