Remote desktop/vnc into a windows computer from a Ubuntu computer

Try Gnome-RDP it should do what you're after (assuming you're using gnome anyway)

"Give NoMachine a whirl.

Moreover, NX also can connect to
remote RDP and VNC servers, relying on
the rdesktop and TightVNC clients by
encapsulating the RDP or RFB session
within the X11 session."