Hello! First post

I first installed Vista on my 2 year old HP Media Center a few months ago and am just now having the need to run Second Life on it (I make a good chunk of my income on Second Life). My laptop has taken a dirt nap.
Here's my question. When I had XP Media Edition on this computer, everything worked wonderfully; even Second Life.
Since installing Vista, my computer/Second Life doesn't recognize the graphics card as sufficient (Not sure which is freaking out about it).
How do I get this machine to run Second Life again???