You probably have sensitive information like bank account numbers and personal documents on your computer. So you password-protect your Windows account and your home accounting files.

But password systems offer scant protection from experienced crooks. There are numerous products on the Internet, many free, that recover or reset Windows, Microsoft Word and popular accounting program passwords, to name a few.

To protect your sensitive files, encryption is the answer. And, the basics of encryption are easy to understand.

First, the encryption program creates a key. The longer the key, the stronger the encryption. Modern encryption is 128-bit or greater. This means there are trillions of possible combinations. This is considered unbreakable at the current level of computer technology.

Keys are used to encrypt and decrypt the data. Without the key, the data look like gibberish. But don't let the word "key" throw you. That is just a password, which you select. Pick a longish one with letters, numbers and symbols, and you're well protected. Use your dog's name, and you're not. It's up to you.

Let's start with Windows XP, which includes encryption abilities. To encrypt a file or folder, right-click it and select Properties. On the General tab, click Advanced. Select "Encrypt contents to secure data" and click OK. Click Apply and select your options. Click OK.

Unfortunately, Windows stores the encryption key with your user account. Anyone who knows your Windows password can access your encrypted files. Or, given a little time, your Windows password, no matter how strong, could be broken. There are numerous tools available on the Web to do just that.

Mac OS X 10.3 and later includes FileVault, which uses first-rate 128-bit encryption. The password is separate from your system password. Your home directory is automatically encrypted and decrypted. To turn on FileVault, open System Preferences. Under Personal, select Security. Click Set Master Password to set a password for each user's FileVault. Click Turn On FileVault.

There isn't much available for earlier versions of the Mac. Try KremlinEncrypt (www. kremlinencrypt.com, $35) or SecretAgent (www.infoseccorp .com, $265).

I recommend using a third-party program to encrypt in Windows. The free Cryptainer LE (www.cypherix.co.uk) creates an encrypted vault on your computer. It holds up to 25 MB of data. Simply create a key and then drag and drop your files to encrypt them.

If you need more space, Cryptainer PE allows you to encrypt 25 gigabytes of data for $45. Other encryption programs include PGP Desktop Home (www.pgp.com, $99), Bestcrypt (www.jetico.com, $60), and PC-Encrypt (www.pc-encrypt.com, $49).

If you're on a tighter budget, consider a ZIP program. ZIP programs compress files so they are smaller. Many offer encryption as a bonus.

WinZip (www.winzip.com) supports 128-bit or 256-bit AES (Advanced Encryption Standard). PKZIP (www.pkware .com) uses 128-bit AES. Both are $29.

One word of caution: Don't forget your password. You could be locked out of your files just the same as the bad guys.

Contact Kim Komando at www.komando.com/contact.asp.