to Nike-it Nike-it and anyone elce who wants to help by grasshopper45

[grasshopper45]

I have an HP Pavilion desktop computer with windows vista home premium 32-bit OS, not to long ago i put in the maximum amount of memory aloud for my operating system. the amount aloud is 4 gigabytes.

now i am thinking about updating to a higher performance graphics card specifically made for 3d gaming and regular gaming. right now i have the NVIDIA GeForce 6150SE nForce 430 graphic card witch is integrated in my PC and has a low 3d and gaming performance score.

i have no VGA slots but i do have some PCI slots, here are the PCI slots i have open. 

PCI Two (One available)
PCI Express x16 One (One available)
PCI Express x1 One (One available)

whats the difference between regular PCI and Pci Express x16 and PCI Express x1?

now with all the information i have provided for you does anyone have any ideas on a good and powerful performance graphic card for my computer?
if so let me know
thanks,
grasshopper45
P.S. recommendations and opinions welcome