One of the great tools we always had for management of our Active Directory Infrastructures is Group Policy. Group Policy is a centralized management tool allow you to control and manage your users desktops. You can control settings from desktop configuration to deploying software. Another great group of policy settings are the Software Restriction Policies. These allowed you control what applications a user could run on their desktop, as solid as software restriction policies were, there was room for improvement. In Windows 7 we have a new way to control applications called App Locker. Take a look at the following screencast for a quick overview of these new and powerful tool built into Windows 7.
If you want to learn more about group policy take a look at the screencast series I did a while back, even though the series is from Windows Server 2003, you can get some good foundation knowledge here: A Blast from the Past: Group Policy and Active Directory Webcast series