KILL IT WITH FIRE! I'm sorry dude but that comp will never run current games ever. 1. Very few games will run on 2gb of ram now & 2. That CPU is so slow it will bottleneck any GPU you put in it. Your best option is to get rid of it & build a new computer
Sorry man, but this is not true.
I have a pc with a Core 2 Duo E6300 @1.86 GHz, 3 GB DDR2 and a GTS 450 and i run most games at high settings @1600x900 with minimum lags. I also overclocked a little the GPU and now I get like a mid-end PC.
A pentium dual core is not SO slow. Yeah, it is a slow CPU, but decent and capable of discrete GPUs. Also a GPU can be buyed not only for gaming, maybe goshet0 needs a low-end GPU but capable of some new tecnologies (DirectX 11, Shader Model 5, OpenGL 4.1 and many others...) or a discrete GPU to watch HD videos.
A pentium dual core @2.2 GHz is a little slower than my Core 2 Duo. So it will NOT bottleneck mid-range GPUs.
PCI Express 1.1/2.0/2.1/3.0 cards are compatible with PCI Express 1.0 slots, but some have issues with it. I experienced issues with a Radeon HD 5670 (with no external power connectors) in my Asus P5LP-LE, which has one PCI Express 1.1 slot. The card didn't show any imput on screen. Then I installed a PCI Express 2.0 card (a GTS 450) with an external power connector and it worked well.
So my suggestion is to avoid graphics cards with PCI Express 2.1 or 3.0, especially if they don't draw power with external connectors, if you aren't 100% sure that the graphics card will work. The performance difference between PCI Express 1.0 and PCI Express 3.0 isn't noticeable if you don't use advanced features or ultra high resolutions.
Since i had issues with Ati cards, i suggest you to get a GTS 450, which is a good PCI Express 2.0 mid-range card. GTX 550 Ti and GTX 650 Ti/non Ti are also good cards, but they are both PCI Express 2.1/3.0 cards, and I'm not sure they will work. These are the best Nvidia GPU you can fit in your system with minimal or null bottleneck by your CPU.
Don't take too powerful graphics card, because your CPU (the Pentium dual core) will bottleneck it. For example, a GTX 670 or a Radeon HD 7850 will be a waste on your pc. A GTX 650 probably will be a waste too, so don't go so high.
If you aren't going to buy a new pc in short times, get a new mid-range GPU. If you are going to buy a new pc in a little time, i suggest you to save your money and keep your 8500GT.
[the GPU i listed are all OK with your PSU]
