Newdev.dll is a standard Windows library involved in the process of adding new hardware to your computer. It's a file that is needed by Windows to work correctly, and therefore shouldn't be moved or deleted.
Every time you add a new piece of hardware to your system, the "Add a New Device" wizard is evoked. The newdev.dll file is part of that system, and as new hardware devices are detected automatically, the newdev.dll system process is active all the time.
Depending on which application is trying to call newdev.dll depends on when you see the error messages. For example, you may see this error on start-up if an application that requires newdev.dll is in your start-up folder, or is called from the registry during start-up. You may also see one of these messages when you start particular applications.
A missing or corrupt newdev.dll file will not cause any significant problems, although because many system processes call newdev.dll you will probably receive many error messages while working on your computer, which can be disruptive and annoying. You may also experience difficulty when adding new devices to your system, and they may not automatically be installed or detected.
The only solution to repairing newdev.dll errors is to replace the missing or corrupt file. The method of repair usually depends on the circumstances in which it went missing. If you started experiencing problems after uninstalling a specific piece of software, reinstalling might replace the newdev.dll file. If you believe that you deleted the newdev.dll file yourself by accident, you can usually find it in your recycle bin, and restoring it from there is an easy process. Alternatively, running Windows Update can restore this file.
If none of these methods work you can try running a system repair from your Windows disk, this will repair and replace any files that are missing. You should also scan your OS for errors, as there may be registry entries left over from uninstalled programs that call newdev.dll