Oops I killed display

Red-faced plea for help! I am running a Dell Dimension under XP and some time ago installed an Inno3D graphics card and disabled the integrated graphics. The display had been playing up lately, needing some fiddling with the card (I blame the wretched Dell screwless card slot) so I was attempting to go back to the onboard graphics. This is where I screwed up! I attempted to enable the Intel graphics and disable the Inno3D card in device manager, rebooted and - presto - no display at all. Guess I forgot something crucial.

I have tried everything I can think of but still no display, although the PC seems to fire up ok.
Any clever suggestions how I can get out of this one???

 

OK - panic over - after much juggling of cables and rebooting, the display has restored itself using the Intel drivers.

Now if someone would like to explain the correct way to do it...