Nvidia - please help

hello everyone, I'm not really new to Linux, but I have been trying to get an Nvidia card to run unsuccesfully and it's becoming really frustrating. I have installed and uninstalled the drivers several times using different methods, including manual install with kernel module compilation and everything, and the latest EnvyNG, with two different cards, both verified in the list of supported nvidia cards, and I always get the same error, the system crashes on start up during the splash screen when I try to boot with the Nvidia graphics card, and if I use safe mode, it gives me an error visible in console mode saying that: init: rcS main process (2640) killed by SEGV signal init: unable to execute '/bin/sh' for rc-default: no such file or directory init: rc-default main process (3976) terminated with status 255 I have to switch back to on board graphics if I want to use my pc. I have really tried for hours and hours and I think I'm gonna strangle someone to blow off some steam. I've tried this with ubuntu Fiesty, Comfusion and currently with Hardy, I know for a fact that these cards work, I just can't seem to pull it off who knows why, and on top of this, my integrated video became really defficient and will not go back to normal. my sistem is: Intel® Desktop Board D946GZIS NVIDIA GeForce 7100 GS pci express 256mb and/or a 6 series turbo cache 128 mb with a dual core 3.0ghz 32 bit processor besides this, everything works great with ubuntu, but as a man, this issue is hurting my pride, putting a side the fact that I can't take full advantage of my graphics accelerator. If anyone could help me, I would be thankful for life and would do anything I could to return the favor.