Visual Studio 2008: Device Security Manager
In my post “How to” Series: Windows Mobile Security Configurations, I said that if you want to deal with the device security configurations you may download the Security Configuration Manager Powertoy for Windows Mobile.(there are some other options as well)
If you have the Visual Studio 2008 Beta 2 installed, you do not need this powertoy anymore. It is part of VS 2008,now. 
Just cradle the device( or emulator) , launch the Device Security Manager and start locking,unlocking and installing device certificates :).
I just noticed Mark Arteaga has collected some resources related to Windows Mobile Security. Check them out.
Links:
“How to” Series: Windows Mobile Security Configurations
Windows Mobile Security resources from Mark Arteaga