Keepass does not encrypt files or folders, it is simply a tool for keeping your passwords safe and organised.
If you installed a program that locked and/or encrypted your files, a solution really depends on the program you used.
If it simply changed NTFS permissions or similar, it is a trivial task. If however you used something like True Crypt, you could have set up full encryption and you will need your keys to unlock.
In any situation, the best case is to re-download the original tool and try to undo the changes you made.
If this is not possible, we really need more information to help you further such as the name of the program you used and/or what you did.