you need to do one of two things to the Windows2000 machine:
1- Enable GUEST account (somewhat insecure)
Open up User Manager:
Start/Settings/Control Pannel/Users & Passwords
Advanced Tab
"Advanced User Management" / press Advanced button
Under "Users", Right click on "Guest" and go into properties and Uncheck "Account is disabled", then apply it.
You should be able to access the w2k machine now.
2- Make an account for the win9x computer. (more secure)
same deal, open up till the Users tab.
then create a new user, the username HAS TO BE THE SAME USERNAME THAT THE WINDOWS 9X COMPUTER IS LOGGED IN AS (or in a multi-user w9x computer, make an account for each user.)
fill in the rest of the form, click ok, apply the changes.
You should be able to access the w2k machine now.