I Need Some Advice For My PC (I'm What You Would Call A Noob)

 Hello, I need some advice on some stuff. I've primarily been a console gamer my entire life, but I have a PC that with a little bit of upgrading could be a decent machine. The only thing I'm really missing is a graphics card. Here is what I got. 
 
HP machine running Vista 64X. I don't see a reason upgrading to Windows 7 due to not wanting to spend the money and even though Vista didn't work at first; the many updates have made it at least work. 
 
It has an integrated graphics card that can hardly run anything. I have steam and play little things like Braid and whatnot but I would like to run Final Fantasy XIV on this since its looking like I'm changing my mind on the Console version and will be playing it on my PC (as long as it doesn't get too expensive.) 
 
It's got 4GB or RAM which I thought would be enough to run anything that I want. 
 
I basically just need some advice on what kind of graphics card I should buy. I thought I would be okay with my MacBook Pro and steam but it primarily has been pretty pathetic. Help me decide on a graphics card (around $100 range) and let me know if I'm being stupid sticking with Vista.     
 
One more thing... my username on steam is mau64 so if you want to add me let me know. I would like to play Team Fortress 2 more but it runs like crap on my Mac.

This is one I'm looking at right now: 
 
http://www.bestbuy.com/site/PNY+-+NVIDIA+GeForce+9800+GT+1GB+GDDR3+PCI+Express+Graphics+Card/8968094.p?id=1218006355798&skuId=8968094&st=graphics%20card&cp=1&lp=8  

That card looks pretty good acc to me, but hopefully other more experienced posters might be able to help you out better. Otherwise, go for that card.

I would save up for that $170 card there, if I were you.  I'm pretty sure Vista can run DX11, and you might as well get a GPU that has native support for it as well, just so you're not left unable to play something in a year that's DX11 only.

Don't buy computer parts or anything from best buy. They're so over priced.
 
Order from Newegg and the like.

I might have just found the one I want 
 
http://www.bestbuy.com/site/VisionTek+-+ATI+Radeon+HD+5450+1GB+DDR+PCI+Express+Graphics+Card/9849611.p?id=1218184698455&skuId=9849611&st=graphics%20card&cp=4&lp=14   

One more question. I'm about to go reinstall Vista on my PC. Should I wait until I get the graphics card or does it matter? 

5770! DO IT 
 
i have one and havent looked back. this thing is a monster

$100 is a terrible starting point, maybe go a bit higher, HD5770. Don't buy a HD5750, lol, your going to regret it. 
 

I got a Radeon 5750 1gb for a pretty solid price of £70. As long as you have a decent processor you should be fine with a 5750.

" @jadeskye: True I suppose, but I still wouldn't recommend getting anything under a 5770. The 5750 costs nearly the same but performs significantly worse. "

" This is one I'm looking at right now: 
 
http://www.bestbuy.com/site/PNY+-+NVIDIA+GeForce+9800+GT+1GB+GDDR3+PCI+Express+Graphics+Card/8968094.p?id=1218006355798&skuId=8968094&st=graphics%20card&cp=1&lp=8   "