Get the MainWindowTitle from a service

Question

I need to get the Main Window title of the processes that are running in my desktop.

I have the following code:

foreach (Process p in Process.GetProcesses())
{
    Response.Write(p.Id + " " + p.ProcessName + "_" + p.MainWindowTitle);
}

The problem is that if I run this code as a *.exe file, I can obtain all the data correctly, but If I run it as a service installed on my desktop, I only get the ID and the ProcessName, but the MainWindowTitle has "" value.

Can someone help me? How can I fix this issue?