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??!