We have replaced the bad drives in a few HP systems (ProLiant DL360 G5), but they continue to show failed. The drives are part of RAID, and I think this might be why they are appearing as failed. The firmware/model is not the same, although they are all HP drives. Is this why they would remain in a failed state? They are new drives, so I don't think they are already bad.
It's all about the controller firmware. Are the systems up-to-date on firmware? If in question, you use the bootable HP Firmwware DVD to bring everything up-to-date.
In addition, if you already have a running operating system on these servers, you may want to obtain the RAID status using the HP Array Configuration Utility.
Sometimes, a drive will not rebuild because there could be a failing drive elsewhere in the array.
If either of the above are the case, the controller/rebuild status will probably be "Waiting for rebuild".
Another option, assuming these servers are healthy, may be a power cycle of the server. Sometimes that can jumpstart the rebuild on controllers with old firmware.
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Install the hpacucli utility for Windows Server 2008 and run the following:
Paste the output into a pastebin or your original question.