When I install Itunes this is the Error message I get verify access npitunes.dll C:\Program Files\iTunes\Mozilla Plugins\npitunes.dll

General installation troubleshooting Important: iTunes installation is successful a majority of the time after completing these troubleshooting procedures. If one step does not resolve your issue proceed to the next.
1. Empty your Temp directory and restart
Windows XP:

1. Choose Start > My Computer (or double-click My Computer on the Desktop).
2. In My Computer or Computer, open the "C:" drive.
3. Open Documents and Settings.
4. Double-click the folder titled with your username.
5. If you see a Local Settings folder, skip to step 10. If you don't see a Local Settings folder, proceed to the next step.
6. Choose Tools > Folder Options.
7. Click the View tab.
8. Select the option to "Show hidden files and folders."
9. Click OK.
10. Double-click Local Settings.
11. Right-click on the Temp folder and choose Delete.
12. In the confirmation dialog that appears click Yes.
13. If you are unable to delete the Temp folder, close all programs, especially those in the Notification area ("System Tray") of the Windows Task bar and repeat step 11.
14. Restart your computer.

Windows Vista and Windows 7:

1. Choose Start > Computer
2. In Computer, open the "C:" drive.
3. Open the Users folder.
4. Double-click the folder titled with your username.
5. If you see an AppData folder, skip to step 10. If you don't see an AppData folder, proceed to the next step.
6. Choose Organize > Folder and Search Options.
7. Click the View tab.
8. Select the option to "Show hidden files and folders." (In Windows 7 this option will be called "Show hidden files, folders, and drives").
9. Click OK.
10. Double-click the AppData folder to open it. If Windows needs your permission to continue click Continue.
11. Double-click the Local folder to open it.
12. Right-click on the Temp folder and choose Delete.
13. In the confirmation dialog that appears click Yes.
14. If you are unable to delete the Temp folder, close all programs, especially those in the Notification area ("System Tray") of the Windows Task bar and repeat step 12.
15. Restart your computer.

2. Completely remove iTunes and QuickTime
For Windows XP, follow instructions in Remove and Reinstall iTunes, QuickTime, and other software components for Windows XP.
For Windows Vista or Windows 7, follow instructions in Remove and Reinstall iTunes, QuickTime, and other software components for Windows Vista.
Note: Songs you purchased from the iTunes Store or imported from CDs are saved in your My Music folder by default and are not deleted by removing iTunes.
3. Install the latest version of iTunes
Once you have completed the above steps to Empty your Temp directory, Completely remove iTunes and QuickTime, and Clean up iTunes installer files on the computer, you can install the latest version of iTunes from http://www.apple.com/itunes/download.
Additional troubleshooting Make sure you have administrator-account access To install iTunes or QuickTime software, you need to be logged in as an administrator on the computer. If you're not sure if you have administrator-account access, contact the owner of the computer or your system administrator.
Get the latest Windows updates The first thing to do when troubleshooting an installation issue on a Windows computer is make sure you have the latest Microsoft Windows updates installed—to get the latest updates, go to the Microsoft Windows Update page.
iTunes and QuickTime software for Windows require Microsoft Windows XP or Microsoft Windows Vista with latest Service Pack installed.
Disable other conflicting software In Windows, some background processes can cause issues for other programs and processes. These conflicts can prevent applications such as iTunes and QuickTime Player from installing. See Using MSCONFIG to troubleshoot conflicts in Windows XP or Using MSCONFIG to troubleshoot conflicts in Windows Vista and Windows 7 for assistance disabling conflicting processes.
Additionally, some third-party security software cannot be disabled using Selective Startup (MSConfig). Because of this, it may be necessary to temporarily manually disable such software while troubleshooting installation. For assistance in configuring or disabling your security software, please contact the manufacturer.
Make sure your folder names don't contain strange characters If the iTunes installer (iTunesSetup) is not responding or appears frozen after launching the installer then the folder where the installer is stored may contain unusual characters. If you notice that the iTunes installer or stored in a folder like this, either rename the folder or move the iTunes installer to another location such as the Desktop before launching.
More help If these steps don't help, you may be able to find a solution to your issue by searching the Microsoft support website.