Make a shortcut to

c:\windows\system32\gpedit.msc /s

This will open up the group policy dialog box.

You can set most of the useful security settings in Windows XP. I recommend looking at

Computer Configuration | Administrative Templates | Windows Components | Terminal Services | Encryption and Security

For timing out a user when inactive, look at

Local Computer Policy | Computer Configuration | Windows Settings | Security Settings | Local Policies | Security Options | Microsoft network server: Amount of idle time required before suspending a session