DEV, Windows Device Driver File (.dev)
The DEV System file format
DEV files can be found on computers running on the Windows operating system or on Mac computers running Parallels Desktop with Windows installed. These files are used to regulate and allow the communication with the Windows installation and a certain amount of hardware devices. DEV files should never be manually altered or even opened when encountered.
Technical details of DEV files
Certain device drivers are already pre-installed in some Windows installations. If not, they are usually installed using a software CD that comes with the respective hardware the driver is needed for. However, DEV drivers can also be acquired over the internet. After installation, the DEV files can be found in the Windows System folder on a user's computer. Do not attempt to open or even alter DEV files!