Question

I want to check if a specific application run on the same computer .

Answer 1

If you know the process name then you can run following code:

Process[] proc = Process.GetProcessesByName("MyApplication");
if(proc.Length== 0)
{
    // No process with name "MyApplication" is running
}   

In case your application supports multiple instances then proc.Length will give you the number of instances running on the system.