Hi Friends

I would like to know if there are Applications which can be used for remotely accessing and Controlling Nokia N900 from a PC (either a Windows or Linux machine using Keyboard and Mouse)

I'm sorry if I had missed any thread which already has this information, but I can promise you I had taken sincere effort in browsing through most of the Threads but could not find much info on this.
On the Contrary there were a lot of threads on how to access a PC desktop remotely from N900. I'm more interested to have info on whether we can do the opposite that is remotely access and control Nokia N900 from a PC

Thanks in advance for the help

Well, if you discard the GUI, the easiest way to do that is to install SSH Server on your N900 and then connect to it from your PC... There is also VNC for full GUI access (x11vnc, I think it's in testing atm.)