i m developing a application for administrative purpose, it's developed completly but now i m stuck with hiding process from taskmanager, because my application monitor the users activity and send reports to admin, i have hide the application but i m not able to hide the process from task manager.
You can not do that. You can rename the EXE file so that no one can know what the process is.
you probably want it to run as a windows service that way it shouldn't appear as an application in task manager and in the processes it will just be one of many svchost.exe processes.
You can't reliably do this. You could use a virus-like technique to hook into the Windows kernel, but your application is liable to be blocked by a virus scanner.
If you're unhappy with users closing your application, why not remove local admin rights from your users and run your app as a Windows service? Windows will then stop them from closing your app.
Create a service / run the application under another user. A non-administrator can not see processes belonging to other users, thus not your app.
Read up on rootkits and techniques used to hide windows processes. http://www.amazon.com/Rootkits-Subverting-Windows-Greg-Hoglund/dp/0321294319
Also a good read from Mark Russinovich http://technet.microsoft.com/en-us/sysinternals/bb897445.aspx