Network Tools wanted

I am after a few network tools (freeware hopefully)

1) I need to see who is currently using files or directories on a windows 2003 server

2) I have two hard drives (about 120Gb) with similar data on, Ones newer than the other. It would take to long to manually see which files are different so a tool to automatically compare would be fantastic.

3) In a Microsoft 2003 network it is recomended to disable network messenger because it leaves you open for getting popup spam from the WWW. Is there any decent freeware that an IT Adminstrator could use to display a pop up on a users screen.

If I had all 3 of these I would be over the moon and it would save me a lot of time so I have given a high amount of points for this.