your card does not have DX10 capability... but VISTA doesn't have a DX10 title available yet.
Your video card is more than enough to run Vista in all its goodlooking...goodness.
I would be more concerned about the amount of memory you are running, and perhaps your CPU.
You need at the very least 1 GB, if you plan on gaming 2 GB and aparently there is a sweet spot at 3GB.
What are the rest of your system specs?