I'll ask the disk question first:
I have 2 WDC hard disks, one a SATA and the other an IDE, both with 160 GB of storage. I had the IDE disk initially, but since I already had the DVD-ROM connected as the other IDE device, I installed the SATA disk( I should have gone for SATA initially

). OF course the server's installed on the IDE drive. The IDE disk has started giving disk errors such as:
a). A disk read error has occurred. Press C+A+Del to restart. Restarting does not help and I end up doing a chkdsk /r using the OS CD to get the computer running again.
b). When I attempt to mirror the system (C) drive with unallocated space on the SATA disk, it goes upto 15% then stops. Disk Management shows that Disk 0 is at risk and I have to hit reactivate disk to get things moving again. But, I am able to mirror the other volumes i.e. D and E (the ones on the IDE drive)
Looking up Event Manager comes up with a rather ominous message on the lines of " \\Device0\ has a bad block".
The defrag tool shows many fragmented files. Defragging it hasnt made a difference.
Does this spell doom of this hard disk??
Now, the ASR question:
Let's say the disk containing the OS failed and I already had another disk installed on the computer before the disk failed. I then put another disk in the computer. How would the computer which disk it should restore itself to. I havent actually performed an ASR before, hence this question.
Help's greatly appreciated.