Hi, Goldie! TrueCrypt is a terrific free, open-source program that can encrypt folders or entire drives. Because encryption requires a password, it locks out access to anyone who doesn't have the password. However, TrueCrypt does not provide password protection *without* encryption.
If all you need is password protection, you could try Folder Lock, which is NOT free. Be sure to get the trial version for testing if you want to try Folder Lock.
A program such as folder lock will prevent the casual intruder and the lazy hacker. However, a determined hacker will still be able to view your files. Using TrueCrypt, even if the data is captured, it's virtually impossible to crack the encryption. Encrypting and decrypting files will cause a slight reduction in file access time, but TrueCrypt is very efficient.