HDD GURU FORUMS

Hello everyone, I am new, I would like to know what you recommend to start working on recovering hard drives, for now I just want to be able to make them have 100% life again, I have hard drives and I get many drives that are without bad sectors , but with 0% life, therefore they no longer serve me for windows and I would like to learn how to place it at 100% to be able to install the operating systems again. can you help me

Used/failed drives coming in and be refurbished for further use is not a good idea. The drives will not work reliably enough, where the customers will be happy.
To use those drives "as parts" for data recovery purpose, then yes, that is feasible.
To learn data recovery, read this forum and HDDOracle (if you can) from A to Z, learn about hddsuperclone, then you can invest in more advanced tools.