Photos on hard drive have automatically converted to an unknown extension (.rjtywsg). They were mostly JPGs or PNGs, are they corrupt?

There are several reasons for a file to convert into different file type or extensions. The main reason for such change could be an infection caused due to virus or malware attack. If the files are infected or converted to any other formats, it is recommended to scan the drive with an antivirus program.
You could use Remo Recover 5.0 software to recover data from the storage device, there are chances the software might be able to recover files before this format conversion.

Here is a step by step video tutorial for your reference: How to recover lost photos using Remo Recover Windows? Or How to recover lost photos on Mac?

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