"First. Im running v8.5 server 2003 and win 2000 on the workstations. when someone logs into windows (the domain controller) then launches filemaker from the desktop. If you go into the pref tab there username shows up. I noticed you can change this and go into a someone else's record by putting in that persons username. What's the scripts that allow this and prevent this."
The user name preference setting is completely independent of what a user does to log into windows or to log into filemaker pro for that matter. It's simply a setting that identifies a particular installation of filemaker pro. In scripts, the function Get(UserName) will return what ever text was entered into this text box. It sounds like whoever designed your database is using this preference setting to keep users from accessing each other's records. As you have discovered, this can be easily subverted by changing this preference setting. It might work better to check the Account Name (Get(AccountName)) instead of the user name as this is part of how Filemaker controls access to a file.
"also When a report is printed on the bottom of the record it displays the date. now you can't just delete the date cause its locked. But if you go into the windows control/clock you can change it that way. Is that where filemaker pulls it from."
This is a feature that is completely up to the person who designed the layout. It sounds like the layout designer put special layout text ("//") that puts the current date on the report. If so, then you are correct that Filemaker is getting the date from the system clock. If you want the date to be editable, you will need to modify the layout and database tables to that you can place a date field on your layout.