If you're using the latest version, 3.4.xx, you cannot because the passwords are encrypted.
If your member knows his username, instruct him to reset his password at the password.asp page (on this site it's http://forum.snitz.com/forum/password.asp) and to follow the instructions. He will need his username and email address that he used to register.
Some of my members also forget their username, email address, etc...
What I do when they want their password and they're a little slow on the technology is I change their email address to my address, then sign in as them and click "fogot password". I then change it back to their email address and send them their password.
It's an easy way around the encryption and getting your members what they want.