What I should store when I encrypt a folder ?

Hi

I previously encrypted a folder but windows was lost and I had to install new windows however I could not access the encrypted folder. Likely I had another backup. So is there a key or something I should store just in case I need to decrypt the important folder after this user is lost?

Thanks

Windows 11 -> Manage user certificates (Control Panel) -> Personal/Certificates -> Pick the one that says "Encrypting File System" -> Right click -> All tasks -> Export

On a new system / new user, it's preferable to import this certificate before starting encrypting folders/files; otherwise, you might end up with two certificates that you need to back up.

As far as using bitlocker or device encryption, BitLocker will prompt you to save a recovery key as well as store a copy of that key in the users MS account (if he uses one). In Windows Home, device encryption is turned on by default when using a MS account. Any other encryption software, I can't help you. Sorry.
If I was going to use encryption I would become very familiar with whatever software I chose to use before encrypting any data so I would be prepared for whatever circumstance that might arise.

Personally, The stuff on my drive is boring and of zero use to anyone who might get access to it so I've not made myself familiar with other encrypting software. I see encryption as pointless and just one more thing that can go wrong so I've stayed away from it.

You can use a normal software to encrypt the folder, Veracrypt, if you intend to use it or 7zip for a quick backup.

Since you are encrypting individual folders, I am making the assumption that you are using EFS (Encrypting File System). This is slightly off topic, but be aware that EFS does NOT play well with networking. If you have a home network and need to access files that you are encrypting with EFS, it won't work. This has been a problem for as long as EFS has existed (decades).

I gave up on EFS a long time ago but tested about 2 months ago and confirmed the EFS issues still exist.

While I only have a relatively small subset of data that I need protected, I gave up on EFS and switched to whole disk BitLocker encryption and this works great for me. Every single system I own has BitLocker on the C: drive and often on other drives as well.