how to hide a running application or how to make it to run in background so that no one else could know what is currently running in this system?

regards
sancmdowplease be more descriptiveSorry, I assumed you would Google it.

Quote

Cmdow is a Win32 commandline utility for NT4/2000/XP/2003 that allows windows to be listed, moved, resized, renamed, hidden/unhidden, disabled/enabled, MINIMIZED, maximized, restored, activated/inactivated, CLOSED, killed and more.

Cmdow is 31kb standalone executable. It does not create any temporary files, nor does it write to the registry. There is no installation procedure, just run it. To completely remove all traces of it from your system, delete it.

Cmdow was written with batch file programmers in mind. PARTICULAR attention has been paid to Cmdows output MAKING it easy to process with the 'FOR /F' command found in NT4/2000/XP/2003.

CHP.EXE is a very simple program utilising the Win32 CreateProcess API to silently launch GUI and console apps in a hidden window. CHP is free open source software.
Usage
CHP yourapp arg1 arg2 arg3 ...

Prefix your original commandline with CHP.

For EXAMPLE:-
CHP notepad <-- runs notepad.exe in a hidden window
CHP notepad /p "New Text Document.txt" <-- silently prints a text file
CHP cmd.exe /c ""d:\my batch file.cmd" arg1 "arg two"" <-- runs a batch file in a hidden window

Sorry, I assumed you would Google it.