You might need to give us a bit more information. I'm just guessing, but it sounds like your friend's system has W2K on it, and your system is Win9X, and you can't access a share on his machine because his machine asking you for a password. If he wants to share with you he needs to either enable his guest account (disabled by default - not recommended because of security issues, especially if he's connected to a LAN or WAN or Internet) OR he has to create a user on his system which has exactly the same user name and password that you use on your system. (If you don't have a profile like this, you'll have to create it on your machine.) The user account he creates for you can be set up to allow just about as much, or as little, access to his system as he wishes.
Hope this helps.
Regards,
Jim