Need help with degraded raid 5

You probably corrupted your array.

You were having no problems with your 3-disk array, until you re-inserted the 4th disk which you temporarily borrowed from the array. However, the special 'metadata' marker is still on that disk and once you re-inserted it, the RAID BIOS might not know it contains stale/old/bad data and needs to be rebuilt.

Questions for you:
- what did you do with the HDD you removed, did your mom write to it? Changed anything?
- once you re-connected it to the array, how did the RAID BIOS detect your array, with 3 disks or with 4 disks (complete) ?

You might still be able to correct this by recovering using only the 3 drives, but if you have written to the drive you removed, and then put it back in the array and order a parity rebuild, you might have destroyed all data because corrupt data is used to rebuild the array, therefore corrupting the other disks too.

I can't tell if this is the case, it depends on what you actually did with that "contaminated" disk you put back in, and how the RAID engine responds to that, since it still recognises that disk to be part of the array (maybe not even detecting it was gone for some time, with data changed on the disk which should trigger a rebuild).

Also remember that RAID5 is complicated technology and most certainly not a backup. The best advice i can give you is... buy an additional single 1TB, 1.5TB or 2.0TB drive and use it for backups.

If you want to have any chance at recovery i need to know in more detail:
1) what you exactly did what that one disk
2) what kind of raid engine you are using (i assume onboard RAID)
3) you "deleted the MBR" could you explain that in more detail since RAID engines do not care about MBR.

Should recovery be possible, you can use FreeBSD to recover your data. It can read from undamaged NTFS partitions. Should the onboard data be damaged its possible the recovery won't work, at least not the way i do it.

I also want to say that this kind of recovery procedure might be tiresome and long. You will need to spend some time on it. So you also have to consider the importance of the information on it.