Unfortunately, I can't make a informed decision due to the lack of information here. We need more information to give more accurate and informed suggestions.
-RAM (How much? DDR2? or DDR3?)
-Games - What games do you plan to play?
-Monitor Resolution - What resolution to you plan to play your games at?
Assuming this is your PC:http://support.dell.com/support/edocs/systems/inspd530/en/OM/HTML/appendix.htm
Unfortunately, even after taking the max power draw of the GT440 at 65 watts and the fact the motherboard does have a PCI-E slot. Dell prebuilts are notorious for using cheap power supplies. Even assuming you could run the graphics card, you would have a rather poor performance to money ratio due to the low performance of the card itself. Your better off getting a AMD 7770 (80watts), however it requires slightly more power.