Various rantings about my PC, what do I need to run games?

I've had this computer for about 2 years, and I'd really like to start gaming on it. 
I don't need it to be top of the line or anything like that. But I would like to play current games on it.  
I would like to run things on the default settings, I don't want to have to turn down the settings.
My Power Supply recently crapped out. So I know I need to fix that.  But while I'm doing that, I figure I should tune it up to play games.
 
Here are my specs as of right now.

(From the General System Properties)
AMD Athlon 64X2 Dual Core Processor 5200+  (2.611 GHz)
2.61 GHz, 2.43 GB of RAM
 NVIDIA GeFORCE 6150 SE. 
Running DirectX 9
 
 I did some research around, and it seems like everything is fine except for the video card. Apparently the 6150 SE is pretty bad. 
What video card would you recommend? I don't want to break the bank, but I want something decent.  I have a widescreen monitor if that affects anything.
 

Sorry that this seems so damn random. I'm trying to put as much info in as possible, and I'm really not sure what to ask.
Is there something else I should be looking at besides the recommended specs to run a game? 
 
Anyways, if you're still reading this, any help would be appreciated. I am new to this, and don't want to mess things up too badly. 
Thanks.

I've had this computer for about 2 years, and I'd really like to start gaming on it. 
I don't need it to be top of the line or anything like that. But I would like to play current games on it.  
I would like to run things on the default settings, I don't want to have to turn down the settings.
My Power Supply recently crapped out. So I know I need to fix that.  But while I'm doing that, I figure I should tune it up to play games.
 
Here are my specs as of right now.

(From the General System Properties)
AMD Athlon 64X2 Dual Core Processor 5200+  (2.611 GHz)
2.61 GHz, 2.43 GB of RAM
 NVIDIA GeFORCE 6150 SE. 
Running DirectX 9
 
 I did some research around, and it seems like everything is fine except for the video card. Apparently the 6150 SE is pretty bad. 
What video card would you recommend? I don't want to break the bank, but I want something decent.  I have a widescreen monitor if that affects anything.
 

Sorry that this seems so damn random. I'm trying to put as much info in as possible, and I'm really not sure what to ask.
Is there something else I should be looking at besides the recommended specs to run a game? 
 
Anyways, if you're still reading this, any help would be appreciated. I am new to this, and don't want to mess things up too badly. 
Thanks.

What's the max resolution on your monitor?
 
I would just pick up a ATI 4850 or 4870 depending on how much you want to spend.

 Invest in a 64-bit OS now if you haven't already (I'd suggest Windows 7) and pump it full of RAM - I'd say 6 GB, which should set you for the foreseeable future and insure that it will never be a bottleneck - because it's usually the cheapest bottleneck to eliminate.  
 
As for the power supply, take a look at what your new video card recommends and take it a few steps higher. As for the video card......
 
just look up the best rated budget (but of "medium" quality and performance) video card on review sites like Tom's Hardware or Anandtech. They typically conduct reasonable and well informed benchmarks. Gunning for high end cards has historically been a waste of money for years now. Hell, I'm still running a three year old card that I paid about $120 for and it performs spectacularly in anything that isn't Crysis. ;)