TrustedInstaller.exe takes a lot of CPU

Windows Server 2008 will run TrustedInstaller.exe shortly after rebooting after installing the monthly Windows Updates.

The program will take up ~75-100% of a CPU core for up to 30 minutes or more, as it is running the malicious software removal scanning code.

While this is running on a single-core machine, certain programs or services will not work properly, such as SQL Server -- most single-core SQL Server installations will not take connections while the above is running.

So, plan accordingly. After your first reboot, expect a CPU hog.

If you're running on Amazon EC2, it may be wise to make sure to boot up as a dual-core server after installing updates, and then back down to a single-core once TrustedInstaller is done hogging a core.

You aren't alone. Others are having issues with TrustedInstaller.exe.

This one looks like the best: TrustedInstaller.exe Process 100% High CPU Usage in Vista Task Manager Fix. Hope that what's true for Vista will do for Win 2k8.

You can also try clearing solution and problem history in the "Problem Reports and Solutions" control panel, and turning off problem reporting for all users. It appears that TrustedInstaller.exe periodically polls for solutions for any logged "problems" (i.e. application or system crashes) and this tends to be resource-intensive.

Don't do any of this, just make sure you're running the latest Service Pack.