You'll have no socket compatibility problems with a PCIex16 graphic card, but it will have to be low powered because of your 220 watt power supply and it will have to be a low profile graphic card to fit in your case.
I have a Dell Vostro 1720 lap warmer with an Intel G45 GPU... I travel to the middle of nowhere often and need my gaming entertainment. The current card barely allows me to run games on 'Low' graphic settings on the lowest resolution setting. (ie Bioshock 2, Crysis, etc.)
Which video card would be best to stick in this laptop? (considering size, power needs and cooling). RAM's not a problem, came with 4 gig.