1. Right-click on the start button in Windows. When your options pop up, select explore to open Windows Explorer. In the left panel of Explorer, navigate to the system folder for your version of Windows. If you're using a 32-bit version of XP or Vista, this is C:\Windows\System32. In 64-bit versions of XP or Vista, it's C:\Windows\SysWOW64. In 2000 and NT, it's C:\WINNT\System32. In 95, 98 and ME, it's C:\Windows\System.
2. Left-click on the system folder in the left panel to display all of its contents in the right panel. Browse through the right panel until you see nv4_disp.dll, then right-click on the file and select delete from the pop-up options. This moves the file to the recycle bin.
3. Left-click on the start button in Windows and click the run button on the start menu. In the run window, type 'cmd' and then click the run button. This will open the command prompt window.
4. Type regsvr32 /u C:\Windows\System32\nv4_disp.dll in the command prompt, but make sure that the file path specified is the right file path for your version of Windows. In this example, the file path for 32-bit versions of XP and Vista is used. If you're using a different version, refer to the system folder file paths listed in step one and substitute the path for your version in this line. Once you've typed this command, press enter to unregister the .dll from your system.