How to open encrypted folder after windows lost ?

When you select to encrypt a folder and this windows with admin user is lost is it possible if I installed new windows 11 and created same user name with same password to open the folder ?

If you are referring to using Windows' "Encrypt contents to secure data" feature (NTFS Encrypting File System), available in Windows Pro editions, the answer is no; you cannot access the encrypted contents using the same account name with the same password.

To read the encrypted contents using a different account or computer, you need to export the encryption certificate from the account that you originally used to enable the option (which you seem to no longer have). You can do this by going to Control Panel -> Manage User Certificates -> Personal/Certificates. Using EFS without exporting the certificate will typically result in permanent loss of access to the encrypted contents in the future, as there is no other way to decrypt the contents if you lose access to the account without the certificate.