First of all reboot and boot up with -x option (safe mode prevents from loading specific drivers, so you won’t see any glich or window content disappear –NOTE– if you can’t surf on internet in safe mode you have to download the programs in normal mode (i know, it’s stressful but you have to do it)) go on /System/Library/Extensions and copy NVDANV50Hal.kext and NVDAResman.kext to your Desktop.

Now right click on NVDANV50Hal.kext and select Show Package Contents and then go in Contents.

At this point you have to edit the file info.plist modifying it as follows:

<key>IOPCIPrimaryMatch</key>
<string>[Your graphic card ID goes here( it should be: 0x062210de]</string>

To know what’s your graphic card ID just open System Profiler and select Graphics/Display

Now replace [Your graphic card ID goes here( it should be: 0x062210de] with <Device ID in System Profile>10de.
You should get something like this:

<key>IOPCIPrimaryMatch</key>
<string>0×062210de</string>

Do the same steps of above with NVDAResman.kext

Downlaod Kext Helper and install it (if you have installed an iPC distro with all the applications you don’t need to download it, just look in applications).
Drag the *.kext you have on your desktop in the main window of Kext Helper and insert the password to proceed with the installation of the extensions.

Once you have installed kexts, downlaod OSX86 Tools, and install it again as you did before with Kext Helper.

Open OSX86 Tools and press Add EFI Strings/Boot Flag.

Select GFXString and in the dropdown list choose Custom GeForce (the last one).
Enter the name. (Ex: “nVidia Geforce 9600 GT”); –> Choos VRAM size (In my case 512); –> Now the output (My card has two DVI output).
Don’t close OSX86 Tools. 

Add this string to the file: /Library/Preferences/SystemConfiguration/com.apple.Boot.plist

<key>device-properties</key>
<string>[OSX86 Hexadecimal EFI String goes here]</string>

Now copy the OSX86 Hexadecimal EFI String to: /Library/Preferences/SystemConfiguration/com.apple.Boot.plist Probably you will have to change permissions to edit the file.
Ex:

<key>device-properties</key>
<string>6c0200000100000001000000600200000d000000…</string>

You can apply the string using OSX86 tools, but i had some missing scripts, so i had to do it manually.

Cross your fingers and Reboot .
When you log in you should have a completely 3d accelerated desktop.

If something doesn’t work do the same with NVDA40.kext and so on… if you have a NVDAXXPPC.kext try to modify it too.