if your only using the passwords for verification (i.e. do not need to know what they are), try using a one way hash on them - store the hash not the password. Hashing is good, if someone gets your db, they don't get the passwords
If not, there are pleanty of RSA etc free encryption code avalible for ASP free. Try www.programmersheaven.com or asp101.com etc. SEARCH GOOGLE??!
Here's an encryption algorithm I've used for sensitive data. It's not 100% crackproof, but is extremely difficult to decypher without the encryption key. Let me know if it works for you. It's my own version of the Virgenere encryption scheme, and has served me well.