Hi,
Sounds like the partition info got blown out. I would put the HD back in the slot it was in and In disk manager, right click on the drive, and select the make the partition active option. If it's not an option or does not work, then put in a new drive, format it and test to make sure that it was the drive and not the controller, cable, or other problem with the system. Consider 3rd party partition recovery software if you want to pursue that road. Search for "recover partition" on EE for many suggestions.
If the HD really is bad, I would install a new HD, make sure it's the same drive letter as the old one, and do a reinstall of exchange. This method will install exchange in a way that it's ready to accept a restore of the info store when the reinstall is finished:
http://technet.microsoft.com/en-us/library/aa997239(EXCHG.65).aspx