Is not my Icloud account is registered with Apple server? Therefore by just wiping and formatting Hard drive,still i should be able to operate my Icloud and thus can locate the device?
The icloud account has nothing to do with the device, if someone format's the computer, or removes your icloud settings from the computer, when you dial into www.icloud.com you wont be able to track the device anymore.
However, in order to track the device by logging into the website the computer has to have an active internet connection.
I would think if the criminal is an idiot he will just take it home and start using it without any idea it can be tracked and get onto the internet. If the thief knows better he would format the computer before getting on the internet.