Use Testdisk to recover the partition. This might help anyone having this problem.
Error: Blue Screen Error: Unmountable_boot_volume
Solution:
Step 1:Create a new log
Step 2:Proceed (Select local Hard Drive)
Step 3:Select Intel partition.
Step 4:Analyze current partition structure.
Step 5:Quick search
Step 6:Answer No (N) for Vista partition.
Step 7:Make sure [WinXP] is *=primary bootable and [Data] is P=Primary.
Step 8:Highlight the *-Primary bootable partition
Step 9:Select [Write]
Step 10:Confirm partition write [Y]
-Reboot