This handy utility can help you find out why.  It is from http://www.iarsn.com/download.html

     TaskInfo for Win95/98/ME/NT/2000/XP shows in real time information about all running processes and threads including ring0 VxD threads. For each process information includes threads, CPU usage, scheduling rate, path, open files, command line, environment variables, memory usage, DLLs, Version information and other.

     It can run new processes and force termination of badly behaving processes. Change Process priority. Command line commands to start new process with selected priority, change priority of running process and kill process. Reboot or Shudown System. Start Just in Time Debugger for running process and other ...

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