Vista...is it a 32 bit version or 64 bit.

Hi.
I dont' work for bestbuy, so i can't tell what the hardware inside this pc is, only looking inside the pc or the hardware manuals a technician can work.
However, to know what kind of windows is installed, you don't need to be an expert, Windows XP 32 bits only shows the logo( WINDOWS XP ), unlike Windows XP 64 bits, this appears as:
( WINDOWS XP X64 ) when windows is starting.
Also you can go to START - CONTROL PANEL - double click on SYSTEM, there you will see some of your system specs.

About the Graphics card, the most qualified to tell you that is Nvidea Manufacturer itself:
See for yourself.
http://www.nvidia.com/object/geforce_family.html

Hope this help you.
Good luck.