|Something similar happened to me when I tried to add a secondary IDE drive to a computer that came out of the box with a primary SATA drive. XpUser is correct that "EISA Configured" is supposed to be used for OEM System Restore data, but sometimes Windows gets confused and thinks a real drive is a restore partition. The Disk Management snap-in prevents you from doing anything to any partition that it believes to be a System Restore partition.|
The only way I found to fix it is to use the DISKPART command-line utility to reset the partition type back to a normal partition, not an EISA (restore) partition. As an added bonus, this will leave any data that was on the partition intact. Here's how:
Use at your own risk - Microsoft's help file for the SETID command suggests that only OEM's and IT Pro's should be meddling with this. You can mess up your partitions if you use the wrong ID! Search for MBR Type Byte codes online or go to http://msdn.microsoft.com/en-us/lib... first to find the right one for your kind of drive. The code for regular NTFS drives is 07 (same as IFS in the linked page), but yours may not be that type.
Start > All Programs > Accessories > Right-Click Command Prompt > Run as Administrator
SELECT DISK [id of the disk with the errant partition]
SELECT PARTITION [id of the errant partition]
(Confirm that the ID is 27. 27 is the hex code for OEM reserved partitions.)
SET ID=[correct code for your partition]
You can now use either DISKPART or the Disk Management snap-in to assign a drive letter to the newly unlocked volume.