Even if you only have one user in win2k, there are GROUPS of users that exist automaticly called Administrators, Power Users, Users, etc. I doubt you're being hacked.
Yes, I just checked, all of those are the default file permissions for files in win2k. THIS IS NORMAL!! YOU ARE NOT BEING HACKED! Zone alarm isn't detecting anything because there's nothing to detect.
Your windows directory permissions are set so that certain groups (IE Administrator, Power Users, SYSTEM and users) have certain rights. That SYSTEM group is for the operating system's use, so that it can get in and get the files it needs from its own directory. Don't delete these groups or permissions! You could cause a heck of a lot of trouble!