Here's a batch file for lazy people like me to manage my usernames and passwords. Just create a batch file and paste the following text into it.
SET /P username=Enter username:
e:\xampp\apache\bin\htpasswd.exe -m users.pwd %username%
I've only tested this on win2003, I guess it should work on win2000 and winxp as well. BTW, don't forget to change the path of the "htpasswd.exe" and the name of the password file "users.pwd". NB: The password file must already exist.