Consider the situations which cause a computer to hang up while booting or hang up due to data loss.
Boot Indicator is removed from the first partition:
0000001B0 00 01 ................ 0000001C0 01 00 07 FE 7F 3E 3F 00 00 00 40 32 4E 00 00 00 ...?>?...@2N...
When trying to boot now, an error message like "Operating System not found" will appear. This means that the loader cannot determine which partition is a system and an active partition to pass control to.
It contains all the necessary information about the partition so that if recovery software finds it, it can reconstruct the partition entry in the Partition Table. (see Partition Boot Sector topic for details).
In this case, a new partition would exist instead of the original one. Everything would work properly with the exception that you could not go back to the original partition if important data is still there. If you've created a MBR, a Partition Table, or a Volume Sectors backup beforehand (as can be done with Active@ Partition Recovery and Active@ UNERASER for example), you can virtually restore it and look for your data (in the case it has not yet been overwritten by new data).
Some advanced recovery tools also have an ability to scan disk surfaces and try to reconstruct previously deleted partition information from the pieces of left over information (i.e. perform virtual partition recovery). However it is not guaranteed that you can recover something.
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