Disk1 Unknown Unreadable!!!

I now have another scsi hard disk with win 2003 server on the same system but when I slave the other hard disk, it still shows Unreadable, Unknown. the status of the SCSI disk as shown in Disk Management are as follows:
Disk1
Unknown
Unreadable
My system configuration: ProLiant ML310GI, Pentium (R)4 CPU 2.53GHZ, 1.25GB RAM, x86-basePC, x86 family 15 model 2 stepping 7 Genuin intel 12524MHZ

When the system boots, I see the other HDD from DOS but the second one shows 'Failed', perhaps the reason it doesnt see it.
I have lots of folders and files to copy from the SCSI hard disk. Pls help me, what can I do?

plz send me the solution

Thanks