I have been testing my Dell mini 10v notebook (1024x600 display) with external 1024x768 displays to make sure I could use it with an Impress slide show. I find an interesting difference between LXDE and KDE3.5, which are both on the machine. Both pick up the external displays automatically, but the way they display is different.
Using KDE3.5 the display on the notebook is scaled to 800x600 to fit the left-hand side of the screen. So it is possible to access the panel from either screen.
But using LXDE (using the settings in "Configure your LXDE Desktop">System>Monitor Settings) you can set one to be 800x600 and the other to be 1024x768, but the display is still 1024x768 on both, so the bottom 178 lines are missing from the notebook's screen - making it difficult to access the panel on the netbook's screen. (Not a serious problem as long as you can see it on the external screen.)
Incidentally, I have often used PCLinuxOS in one form or another for slide shows and always found it straightforward, while others using Windows or Macs often seem to have all sorts of difficulties. On at least one occasion I have had to port Powerpoint over to Impress so save the day – only to have the presenter complain that the fonts weren't right!