C:\Documents and Settings\<username>
...should contain the relevant user's filesystem. If I were you i'd copy that entire folder and it's subfolders into a new folder on the new system (e.g. c:\oldpc\documents and settings\...), and then let each user grab their own bits and pieces as necessary.
(your other option is to create new users on the new machine with the same names as the users on the old machine, and then copy the relevant folders from c:\documents and settings into the new machine's c:\documents and settings, however this is more likely to give you a headache if you don't get something entirely correct - e.g. you need to create the users prior to copying the files, etc).
Obviously, the above folder structure isn't exhaustive, and you should go looking for stray files/folders that the users would want if you have no intention of keeping the old hard drive attached in the new machine.
HTH.