Thanks to everyone who participated on these blogs.
I am liking my n900 a little more now that I have RDP back.

So to install first you need root assess: http://wiki.maemo.org/Root_access
then you need to know the location of your .deb file (here i cant help much)

I found one common folder in the "File Manager" "cities" its path is /home/user/MyDocs/cities/
I moved "rdesktop_1.7-maemo1_armel.deb" (https://garage.maemo.org/frs/?group_id=214) to that folder.
in Xterminal I used the "cd" and "ls" commands to locate it.

then I ran "dpkg -i rdesktop_1.7-maemo1_armel.deb" from the "/home/user/MyDocs/cities/" folder and rDesktop installed and it works well.

Now I need to know how to send an F4 key press through rDesctop from my N900 any help?

thanks to the people who do all this stuff.