When you double-click a registry (.reg) file, Windows merrily merges the information from that file into the registry without any further prompting of the administrator. Imagine if you accidentally merged registry changes that could potentially damage the data on the server.
With a simple change to the system, you can modify the way that Windows NT handles .reg files by default and safely avoid this type of problem. Follow these steps:
From now on, when you double-click a .reg file, Windows NT will open it in Notepad rather than merging it into the registry automatically. To merge the file into the registry, right-click it, and choose Merge.