Yesterday I set up a Promise hw raid controller in my FC8_64 system. I ended up returning it but before I removed it I initialized 2 drives into a RAID0 setup. Now that the controller is gone my system is complaining about /dev/mapper. I ended up clearing this by booting into rescue and initializing the 2 drives I had setup with the controller. The system is happy again but when I do an fdisk -l I still show a /dev/dm-0 device. My question is how can I initialize the drives without booting to rescue mode ? And how can I get rid of the /dev/dm-0 device ?

dmraid still shows the 2 devices. I've initialized and formatted both but it won't go away.
# dmraid -r
ERROR: asr: Invalid magic number in RAID table; saw 0x0, expected 0x900765C4 on /dev/sda
/dev/sdb: pdc, "pdc_bicfbbcgbh", stripe, ok, 312450720 sectors, data@ 0
/dev/sdd: pdc, "pdc_bicfbbcgbh", stripe, ok, 312450720 sectors, data@ 0

Update:
I was able to erase the metadata by using:
dmraid -r /dev/sdb -E
dmraid -r /dev/sdd -E

dmraid reports the following now:
]# dmraid -r
ERROR: asr: Invalid magic number in RAID table; saw 0x0, expected 0x900765C4 on /dev/sda
No RAID disks

I'm not sure what the magic number is about but I've managed to remove the raid disks. Still /dev/dm-0 persists on reboots. How do I get rid of this ?

try wiping your mbr....warning this will mean a clean install.....so grab any data with the live cd if you need it now.

boot live cd open shell

Look at the "sudo /sbin/fisk -l" listing. What ID are the partitions? They should be 83.

Also, from "mdadm --misc --help"
So you could run "sudo /sbin/mdadm --misc --zero-superblock <devices>"

Thanks. No data on the drives to worry about. I ended up just doing dd if=/dev/zero of=/dev/[sdx] count=1.

I also found that:
dmraid -rD /dev/ad[bd]

would work also.