Physical And Logical Data Loss
Data recovery companies categorises data loss into 2 different types, physical and logical. The signs for both sometimes overlap, but mostly are independent of each other.
Logical Data Loss
Signs To Look Out For
- files that are corrupted/raw
- previously deleted/formatted/partitioned
- recently install new software/OS
- viruses, pop ups, spy ware and more
What It Means
Files Are Corrupted / Raw File Format
Corrupted/raw files are sometimes the result of bad sectors, viruses or even bad software programming. The files usually aren’t accessible by the usual methods, so good data recovery software is needed.
Previously Deleted / Formatted / Partitioned
If you have previously, formatted, partition and deleted your file, it has not actually been deleted. Rather this space take by the file is flagged to be overwritten in the future. So, as long as you do not continue using the drive or media, your data can be recovered.
Recently Installed New Software / OS 
If you recently installed or reinstalled software or the operating system, there is a possibility that in the process it corrupted files that uses the software.
Also possible is that a software bug or improper installation causes improper saving process, so that when you save, the file is corrupted.
Viruses, Pop Ups, Spyware And More
Viruses, pop ups and spyware can cause corruption to your data, cripple your system to a crawl or even make it refuse to boot properly. These symptoms soetimes do not affect your data directly, but hinder access to it.
