Doing this isn’t natively supported in 2000. Here is an article about it. I have done it by using System.Security. Cryptography in .net and either binary, varbinary, or image data type in the database. You can also convert the bytes to a base64 encoded string in .net and save it in the database in a varchar field. Regardless doing this in .net requires you to encrypt and un-encrypt the data via code each time. (You could write a wrapper around the db object to do this automatically.)
You might want to use something a little more current than SQL 2000. That was released 10 years ago and there have been 2 versions released since then with another version being released in the next few months.