Need help for getting my GT 640 card to work properly

I have a junkDell desktop 540 pc that came with a crappy gts 240 OEM card Windows 7 and a Quad core Proc and 350w PSU.

Im not very tech-smart and Im in a bit of a pickle here. Friday I bought a new vid card called EVGA gt 640 it fits into the vid card slot with no additional power connectors.

I hooked it up and fired up my pc and windows wouldnt load normally,it was weird so I booted in safe mode with networking. I looked online on steps you take when putting in a new Video card to find out I needed the latest drivers from Nvidia for the gt 640 and also remove any nvidia drivers,applications previously installed on my pc.

During the removal,installing procces my PC asked to restart and i did that and thats when windows wsnt loading properley. I was getting a blue screen with lines then windows would boot all weird colors.

I boot up my pc and my windows is stuck in 800x600 resoulution and I cannotfigure out whats wrong. I installed the drivers from nvidia's website. I also put he disc in my PC that came with the EVGA gt 640 and see if that would let me install drivers etc. It wont work. Im stuck in a basic looking windows and I need help bad.

I was smart enough to remove my old drivers and install new drivers after i removed the gts 240. As of now the gt 640 is installed and windows starts but is in a low res basic operatin mode it seems and I have no clue how to get this pc back to normal with my new Vid card.

Please if you can think of anything I can do please help me. Thanks