backup your wallet.dat file and install bitcoin core on another computer.
Overwrite the new wallet file generated with your old wallet.dat file.
Now the it sync the blockchain. If the problem persists, then I'm affraid you forgot your password!
Thnx!
We can't find the file wallet.dat though. We tried several times to create a new wallet and the new password works fine, but when we open the file with the bitcoins the new password wont work. We 100% sure about the password.
It's the problem that the new wallets password ain't compitable with the old wallet with the bitcoins on?
If you password protected the old wallet, you will need the original password for it. If you are trying to use the password for the new wallet, it will not work for the old. It is like two different houses, just because you updated the lock on one doesn't mean the key will work on both.
Before doing anything you definitely need to backup your old wallet.dat. If you don't, you will lose the private keys and any bitcoins associated with them. You don't specify the OS you are using, but you can look up the locations here:
https://en.bitcoin.it/wiki/Data_directoryIf you can't remember the old password, you will lose the coins unless it was something simple (e.g. 123) that you could try to brute force.
